Polycrystalline diamond compact including at least one mechanically-stressed polycrystalline diamond table and methods of making the same

ABSTRACT

Embodiments disclosed herein relate to polycrystalline diamond compacts (“PDCs”) including at least one mechanically-stressed polycrystalline diamond (“PCD”) table having an upper surface that exhibits a compressive stress state. Providing a selected support structure to the mechanically-stressed PCD table and/or generating a favorable stress state in the upper surface of the mechanically-stressed PCD table may improve a toughness and/or a strength of the mechanically-stressed PCD table and the PDC. In an embodiment, a PDC includes a substrate including an interfacial surface and a preformed PCD table attached to the substrate. The preformed PCD table includes an upper surface spaced from a bottom surface that faces the interfacial surface of the substrate. In such an embodiment, the upper surface of the preformed PCD table exhibits a mechanical deflection and a concave curvature induced by deflecting the preformed PCD table toward the substrate. Methods of forming such PDCs including at least one mechanically-stressed PCD table are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/079,101 filed on 13 Nov. 2014, the disclosure of which is incorporated herein, in its entirety, by this reference.

BACKGROUND

Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilized in a variety of mechanical applications. For example, PDCs are used in drilling tools (e.g., cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing machinery, and in other mechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements in rotary drill bits, such as roller-cone drill bits and fixed-cutter drill bits. A PDC cutting element typically includes a superabrasive diamond layer commonly known as a diamond table. The diamond table is formed and bonded to a substrate using a high-pressure/high-temperature (“HPHT”) process that sinters diamond particles under diamond-stable conditions. The PDC cutting element may also be brazed directly into a preformed pocket, socket, or other receptacle formed in a bit body. The substrate may optionally be brazed or otherwise joined to an attachment member, such as a cylindrical backing. A rotary drill bit typically includes a number of PDC cutting elements affixed to the bit body. It is also known that a stud carrying the PDC may be used as a PDC cutting element when attached to a bit body of a rotary drill bit by press-fitting, brazing, or otherwise securing the stud into a receptacle formed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbide substrate into a container with a volume of diamond particles positioned on a surface of the cemented carbide substrate. A number of such containers may be loaded into an HPHT press. The substrate(s) and volume of diamond particles are then processed under HPHT conditions in the presence of a catalyst material that causes the diamond particles to bond to one another to form a matrix of bonded diamond grains defining a polycrystalline diamond (“PCD”) table. The catalyst material is often a metal-solvent catalyst (e.g., cobalt, nickel, iron, or alloys thereof) that is used for promoting intergrowth of the diamond particles.

In a conventional approach, a constituent of the cemented carbide substrate, such as cobalt from a cobalt-cemented tungsten carbide substrate, liquefies and sweeps from a region adjacent to the volume of diamond particles into interstitial regions between the diamond particles during the HPHT sintering process. The cobalt acts as a catalyst to promote intergrowth between the diamond particles, which results in formation of a matrix of bonded diamond grains having diamond-to-diamond bonding there between, with interstitial regions between the bonded diamond grains being occupied by the solvent catalyst.

The presence of the metal-solvent catalyst in the PCD table is believed to reduce the thermal stability of the PCD table at elevated temperatures. For example, the difference in thermal expansion coefficient between the diamond grains and the metal-solvent catalyst is believed to lead to chipping or cracking of the PCD table during drilling or cutting operations, which can degrade the mechanical properties of the PCD table or cause failure. Additionally, some of the diamond grains can undergo a chemical breakdown or back-conversion to graphite via interaction with the solvent catalyst. At elevated high temperatures, portions of diamond grains may transform to carbon monoxide, carbon dioxide, graphite, or combinations thereof, thereby degrading the mechanical properties of the PDC.

One conventional approach for improving the thermal stability of a PDC is to at least partially remove the metal-solvent catalyst from the PCD table of the PDC by acid leaching. Another approach involves infiltrating and bonding an at least partially leached PCD table to a cemented carbide substrate with a metallic infiltrant, and acid leaching to at least partially remove the metallic infiltrant.

Despite the availability of a number of different PDCs, manufacturers and users of PDCs continue to seek PDCs that exhibit improved toughness, wear resistance, and thermal stability.

SUMMARY

Embodiments disclosed herein relate to PDCs including a mechanically-stressed PCD table having an upper surface that exhibits a compressive stress state. Providing a selected support structure to the mechanically-stressed PCD table and/or generating a compressive stress state in the upper surface of the mechanically-stressed PCD table may improve a toughness and/or a strength of the mechanically-stressed PCD table and the PDC.

In an embodiment, a PDC is disclosed. The polycrystalline diamond compact includes a substrate including an interfacial surface. The PDC also includes a mechanically-stressed PCD table coupled to the substrate. The mechanically-stressed PCD table includes an upper surface spaced from a bottom surface that faces the interfacial surface of the substrate. The upper surface of the mechanically-stressed PCD table exhibits a mechanical deflection and a concave curvature induced by deflection of the mechanically-stressed PCD table toward the substrate.

In an embodiment, a method of forming a PDC is disclosed. The method includes providing an at least partially leached PCD table including an upper surface and a bottom surface. The method also includes deflecting the at least partially leached PCD table to form a mechanically-stressed polycrystalline diamond table. The upper surface of the mechanically-stressed PCD table exhibiting a mechanical deflection and a concave curvature induced by deflecting the at least partially leached PCD table.

In an embodiment, a rotary drill bit is disclosed. The rotary drill bit includes a bit body configured to engage a subterranean formation. The rotary drill bit also includes a plurality of PCD cutting elements attached to the bit body. At least one of the plurality of PCD cutting elements includes a substrate including an interfacial surface. Additionally, the at least one of the plurality of PCD cutting elements also includes a mechanically-stressed PCD table coupled to the substrate. The mechanically-stressed PCD table includes an upper surface spaced from a bottom surface that faces the interfacial surface of the substrate. The upper surface of the mechanically-stressed PCD table exhibits a mechanical deflection induced by a deflection of the mechanically-stressed PCD table toward the substrate.

Further embodiments relate to applications utilizing the disclosed PCD tables and PDCs in various articles and apparatuses, such as bearing apparatuses, wire-drawing dies, machining equipment, and other articles and apparatuses.

Features from any of the disclosed embodiments may be used in combination with one another, without limitation. In addition, other features and advantages of the present disclosure will become apparent to those of ordinary skill in the art through consideration of the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the present disclosure, wherein identical reference numerals refer to identical elements or features in different views or embodiments shown in the drawings.

FIG. 1A is an exploded, cross-sectional view of an embodiment including a preformed PCD table and a substrate having an interfacial surface exhibiting a concave curvature illustrated prior to mounting the preformed PCD table to the substrate.

FIG. 1B is a cross-sectional view of an embodiment of a PDC after mounting the preformed PCD table to the substrate shown in FIG. 1A.

FIG. 2 is cross-sectional view of an embodiment of a PDC including a mechanically-stressed PCD table that is attached to a substrate, with only a portion of the mechanically-stressed PCD table and the substrate contacting each other.

FIG. 3 is cross-sectional view of an embodiment of a PDC including a mechanically-stressed PCD table that is attached to a substrate, with only a portion of the mechanically-stressed PCD table and the substrate contacting each other.

FIG. 4 is a cross-sectional view of an embodiment of a PDC including a mechanically-stressed PCD table attached to a substrate with a washer disposed therebetween.

FIG. 5 is a cross-sectional view of an embodiment of a PDC including a mechanically-stressed PCD table attached to a substrate with a thin foil disposed therebetween.

FIG. 6A is an exploded, cross-sectional view of an embodiment of a preformed PCD table and a substrate prior to mounting the preformed PCD table thereto, with a bottom surface of the preformed PCD table and an interfacial surface of the substrate have corresponding patterns thereon.

FIG. 6B is a cross-sectional view of an embodiment of a PDC after mounting the PCD table to the substrate shown in FIG. 6A.

FIG. 7 is a cross-sectional view of an embodiment of a PDC that includes a mechanically-stressed PCD table that is attached to a substrate including two different materials of different modulus of elasticity.

FIG. 8 is a cross-sectional view of an embodiment of a PDC that includes two or more PCD tables attached to a substrate.

FIG. 9 is a cross-sectional view of an embodiment of a PDC including a mechanically-stressed PCD table, a substrate, and a braze layer therebetween that bonds the mechanically-stressed PCD table to the substrate.

FIG. 10 is a cross-sectional view of a PDC including plurality of stacked PCD tables that are attached to a substrate and brazed together.

FIG. 11 is a cross-sectional view a plurality of stacked PCD tables that are brazed together and are not attached to a substrate.

FIG. 12 is a schematic illustration of an embodiment of a method for fabricating a PDC including a PCD table that may be used in any of the embodiments disclosed herein.

FIG. 13A is an isometric view of an embodiment of a rotary drill bit that may employ one or more of the disclosed PDC embodiments.

FIG. 13B is a top plan view of the rotary drill bit shown in FIG. 13A.

FIG. 14 is an isometric cut-away view of an embodiment of a thrust-bearing apparatus that may utilize one or more of the disclosed PDC embodiments.

FIG. 15 is an isometric cut-away view of an embodiment of a radial bearing apparatus that may utilize one or more of the disclosed PDC embodiments.

DETAILED DESCRIPTION

Embodiments disclosed herein relate to PDCs including a mechanically-stressed PCD table. For example, such a mechanically-stressed PCD table may have an upper surface that exhibits a compressive stress state. Methods of manufacturing such PDCs are also disclosed. Providing a selected support structure to the mechanically-stressed PCD table and/or generating a selected compressive stress state in the upper surface of the mechanically-stressed PCD table with its associated pre-load on a cutting edge thereof may improve a toughness and/or a strength of the mechanically-stressed PCD table and the PDC. The PDC embodiments disclosed herein may be used in a variety of applications, such as drilling tools (e.g., compacts, cutting elements, gage trimmers, etc.), machining equipment, bearing apparatuses, wire-drawing dies, and other apparatuses.

FIG. 1A is an exploded, cross-sectional view of an assembly including a preformed PCD table 102 and a substrate 104 exhibiting an interfacial surface 112 having a concave curvature prior to mounting the preformed PCD table 102 to the substrate 104 to form a PDC 100 (FIG. 1B). As will be discussed hereinbelow, the preformed PCD table 102 may be formed using any of the methods disclosed herein. For example, the preformed PCD table 102 may be an at least partially leached PCD table that is substantially free of metal-solvent catalyst, another suitable thermally-stable PCD table, or another suitable PCD table (e.g., an unleached PCD table). The substrate 104 may include a cemented carbide material, such as tungsten carbide, titanium carbide, chromium carbide, niobium carbide, tantalum carbide, vanadium carbide, or combinations thereof that may be cemented with iron, nickel, cobalt, or alloys thereof. For example, in an embodiment, the substrate 104 comprises a cobalt-cemented tungsten carbide.

The preformed PCD table 102 includes an upper surface 106 spaced from a bottom surface 108. The bottom surface 108 may be substantially planar and face the interfacial surface 112 of the substrate 104. The preformed PCD table 102 further includes at least one lateral surface 110 extending between the upper surface 106 and the bottom surface 108. The upper surface 106 of the preformed PCD table 102 may function as a working or cutting surface of the preformed PCD table 102 in the PDC 100 (FIG. 1B). The at least one lateral surface 110 may also function as a working or cutting surface of the preformed PCD table 102 in the 100.

As discussed above, the interfacial surface 112 of the substrate 104 may exhibit a concave curvature. For example, the concave curvature may be a generally spherical concave curvature. The concave curvature of the interfacial surface 112 is defined by a depth d and a radius of curvature C. The depth d and radius of curvature C of the interfacial surface 112 may be chosen such that the subsequent deflection (e.g., bending, deformation, etc.) of the preformed PCD table 102 to conform to at least a portion (e.g., substantially all) of the interfacial surface 112 creates a specific compressive stress state in the PCD table 102 at and/or near the deflected upper surface 106′ of the mechanically-stressed PCD table 102′ (FIG. 1B). The depth d and radius of curvature C of the interfacial surface 112 may be selected so that the preformed PCD table 102 is not over stressed or fractured when the preformed PCD table 102 conforms to at least a portion of the interfacial surface 112.

The PDC 100 is formed by placing the preformed PCD table 102 at least proximate to the interfacial surface 112 of the substrate 104 to form an assembly, and the assembly is placed in a pressure transmitting medium to form a cell assembly. The cell assembly including the preformed PCD table 102 and the substrate 104 therein is then subjected to an HPHT process. The pressure from the HPHT process is sufficient to deflect the preformed PCD table 102 toward the substrate 104 to form a mechanically-stressed PCD table 102′ (FIG. 1B). For example, the HPHT process may be sufficient to cause the mechanically-stressed PCD table 102′ to contact and substantially conform to a portion or substantially all of the interfacial surface 112 of the substrate 104. For example, the HPHT process uses an ultra-high pressure press at a temperature of at least about 1000° C. (e.g., about 1100° C. to about 2200° C., or about 1200° C. to about 1450° C.) and a pressure in the pressure transmitting medium of at least about 5 GPa (e.g. at least about 7.5 GPa, at least about 9.0 GPa, at least about 10.0 GPa, at least about 11.0 GPa, at least about 12.0 GPa, at least about 14.0, or about 7.5 GPa to about 9.0 GPa). In an embodiment, an infiltrant material from the substrate 104 melts during the HPHT process and infiltrates into interstitial regions of the mechanically-stressed PCD table 102′ (FIG. 1B) to form a bond between the mechanically-stressed PCD table 102′ and the substrate 104 upon cooling from the HPHT process. For example, the infiltrant material may include cobalt from a cobalt-cemented tungsten carbide substrate when the substrate 104 is a cobalt-cemented tungsten carbide substrate. Suitable infiltrants and/or substrates that may be used to bond a mechanically-stressed PCD table to a substrate are disclosed in U.S. application Ser. Nos. 13/275,372 and 13/648,913 and U.S. Pat. No. 8,236,074. The disclosure of each of U.S. application Ser. Nos. 13/275,372 and 13/648,913 and U.S. Pat. No. 8,236,074 is incorporated herein, in its entirety, by this reference.

FIG. 1B is a cross-sectional view of the PDC 100 fabricated from the exploded assembly shown in FIG. 1A. The PDC 100 includes the mechanically-stressed PCD table 102′ that is attached to the substrate 104. The mechanically-stressed PCD table 102′ includes a deflected upper surface 106′ and a deflected bottom surface 108′, with at least one lateral surface 110′ extending therebetween. For example, the deflected upper surface 106′ may exhibit a concave curvature and the deflected bottom surface 108′ may exhibit a convex curvature at least partially due to mechanical deflection thereof. In some embodiments, a chamfer 113 may be formed that extends between the deflected upper surface 106′ and the at least one lateral surface 110′. The chamfer 113 may be formed prior to or after mounting the preformed PCD table 102 to the substrate 104. PCD material adjacent to the deflected upper surface 106′ of the mechanically-stressed PCD table 102′ may exhibit a compressive stress state at least partially due to the mechanical deflection thereof. The deflected bottom surface 108′ of the mechanically-stressed PCD table 102′ may exhibit a tensile stress at least partially due to the mechanical deflection thereof. Thus, the mechanically-stressed PCD table 102′ may be stressed similar to a plate in bending. At least a portion of the deflected bottom surface 108′ of the mechanically-stressed PCD table 102′ at least partially contacts and/or conforms to the interfacial surface 112′ of the substrate 104.

In the illustrated embodiment, the deflected bottom surface 108′ contacts substantially all of the interfacial surface 112. In another embodiment, the mechanically-stressed PCD table 102′ is not deflected sufficiently to allow the deflected bottom surface 108′ to contact all of the interfacial surface 112. In such an embodiment, the deflected bottom surface 108′ of the mechanically-stressed PCD table 102′ only partially contacts the interfacial surface 112 of the substrate 104 and a gap may exist between at least a portion of the deflected bottom surface 108′ and the interfacial surface 112.

It is currently believed by the inventors that the compressive stress state of the deflected upper surface 106′ of the mechanically-stressed PCD table 102′ may increase a toughness (e.g., fracture toughness and/or impact strength) and/or a strength of the mechanically-stressed PCD table 102′ and the PDC 100 during use. The concave curvature of the deflected upper surface 106′ of the mechanically-stressed PCD table 102′ may support some or a majority of the cutting load from the mechanically-stressed PCD table 102′ at or near a periphery of the substrate 104 (e.g., pre-load at the cutting edge), which may help prevent additional deflection of the mechanically-stressed PCD table 102′, reduce the likelihood of failure along a cutting edge, and/or reduce vibrations therein during cutting operations.

In an embodiment, the mechanically-stressed PCD table 102′ may be leached to remove a portion of the infiltrant or catalyst material within the PCD table 102. For example, the mechanically-stressed PCD table 102′ may be leached to form a leached region that extends inwardly from one or more of the deflected upper surface 106′, the at least one lateral surface 110′, or the chamfer 113 to a leach depth “d” of about 50 μm to about 500 μm, such as about 200 μm to about 400 μm, about 150 μm to about 300 μm, or greater than about 400 μm.

FIG. 2 is cross-sectional view of an embodiment of a PDC 200 that is formed by bonding a preformed PCD table (e.g., an at least partially leached PCD table) to a portion of a substrate 204 to form a mechanically-stressed PCD table 202 including a deflected upper surface 206. Such a deflected upper surface 206 may exhibit a compressive stress state at least partially due to the shape of an interfacial surface 212 of the substrate 204. The configuration of the PDC 200 pre-loads a cutting edge of the mechanically-stressed PCD table 102′ against the substrate 204, thereby reducing vibrations in the PDC 200 during cutting operations. For example, the mechanically-stressed PCD table 202 may be formed from a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A). The preformed PCD table may be bonded to the substrate 204 which may be formed from the same materials as the substrate 104. The preformed PCD table may be deflected such that the mechanically-stressed PCD table 202 conforms to and/or contacts at least a portion of an interfacial surface 212 of the substrate 204. The substrate 204 further includes one or more additional surfaces that, along with a deflected bottom surface 208 of the mechanically-stressed PCD table 202, define a region 220 into which the preformed PCD table deflects toward the substrate 204.

In the illustrated embodiment, the interfacial surface 212 extends a certain lateral thickness l_(t) from an outer lateral surface 216 of the substrate 204 towards a center of the substrate 204, such as extending radially inwardly. The lateral thickness l_(t) of the interfacial surface 212 may be chosen based on the amount of contact desired between the mechanically-stressed PCD table 202 and the substrate 204 and/or the amount of deflection desired in the mechanically-stressed PCD table 202. For example, the lateral thickness l_(t) of the interfacial surface 212 may vary depending on one or more of the application of the PDC 200, a thickness of the preformed PCD table, manufacturing parameters used to form the preformed PCD table, a diamond grain size of the PCD table, or an amount the preformed PCD table is to deflect. For example, the lateral thickness l_(t) of the interfacial surface 212 may be less than about 47.5% of a lateral dimension l_(D) of the substrate 204, such as more than about 2.5%, about 5% to about 10%, about 10% to about 20%, about 20% to about 30%, about 30% to about 40%, or between about 40% to about 45%.

In an embodiment, the interfacial surface 212 of the substrate 204 may also exhibit a concave curvature that exhibits a depth and a radius of curvature. The depth and the radius of curvature may be determined by extrapolating the interfacial surface 212 to form a substantially continuous interfacial surface similar to the interfacial surface 112 shown in FIGS. 1A and 1B. The depth and the radius of curvature are chosen such that the mechanically-stressed PCD table 202 exhibits a selected compressive stress state along the deflected upper surface 206 after being bonded (e.g., brazed, metallurgical bonded, HPHT bonded, diffusion bonded, etc.) to the substrate 204. Optionally, as will be discussed later, the mechanically-stressed PCD table 202 does not need to be bonded or to the substrate 204. In other embodiments, the interfacial surface 212 of the substrate 204 may also exhibit a substantially planar topography.

As previously discussed, in addition to the interfacial surface 212, the substrate 204 may exhibit one or more additional surfaces. For example, the substrate 204 includes an inner lateral surface 214 and an inner surface 218 that partially define the region 220 into which the preformed PCD table used to form the mechanically-stressed PCD table 202 deflects during HPHT bonding thereof to the substrate 204. In the illustrated embodiment, the inner lateral surface 214 extends from a radially inner most edge of the interfacial surface 212 towards a bottom surface 228 of the substrate 204 in a direction that is substantially parallel to the outer lateral surface 216. However, in another embodiment, the inner lateral surface 214 of the substrate 204 may extend at an oblique angle relative to the outer lateral surface 216 of the substrate 204. The inner surface 218 extends radially inwardly from a portion of the inner lateral surface 214 that is remote from the interfacial surface 212. The inner surface 218 may exhibit a continuous and substantially planar surface. However, the inner surface 218 may exhibit other topographies, such as a convex or concave curvature.

The PDC 200 may be formed by placing the bottom surface of the preformed PCD table, which, in an embodiment, may be initially substantially planar, adjacent to the interfacial surface 212 of the substrate 204 to form an assembly. The assembly may be placed in a pressure transmitting medium to form a cell assembly. The cell assembly is then subjected to a controlled HPHT process using any of the HPHT process conditions disclosed herein. The pressure and temperature of the HPHT process is sufficient to deflect the preformed PCD table toward the substrate 204 such that the mechanically-stressed PCD table 202 at least partially contacts the interfacial surface 212 of the substrate 204 and is bonded to the substrate 204 in a controlled manner. In an embodiment, an infiltrant material from the substrate 204 melts during the HPHT process and infiltrates into interstitial regions of the mechanically-stressed PCD table 202 to form a bond between the mechanically-stressed PCD table 202 and the interfacial surface 212 of the substrate 204 upon cooling. For example, the infiltrant material may include cobalt from a cobalt-cemented tungsten carbide substrate. Suitable infiltrants and/or substrates that may be used are disclosed in U.S. application Ser. Nos. 13/275,372 and 13/648,913. In other embodiments, the substrate 204 may be brazed to the mechanically-stressed PCD table 202. For example, suitable brazing techniques are disclosed in U.S. Pat. No. 8,236,074.

Because the substrate 204 only contacts the mechanically-stressed PCD table 202 along a limited portion of the mechanically-stressed PCD table 202, the infiltrant material from the substrate 204 may only be present in regions of the mechanically-stressed PCD table 202 proximate to the interfacial surface 212. As such, at least some of (e.g., a majority of) the interstitial regions of the mechanically-stressed PCD table 202 that contacts the substrate 204 may be unoccupied by the infiltrant material (e.g., from the substrate 204). However, after bonding to the substrate 204, the mechanically-stressed PCD table 202 may be leached to a selected leached depth from one or more of the deflected upper surface 206, the at least one lateral surface 210, or the illustrated chamfer 213, as previously described with respect to the PDC 100 of FIG. 1B.

The resulting PDC 200 includes the mechanically-stressed PCD table 202 that is attached to and supported along an outer peripheral edge of the substrate 204. PCD material at and/or near the deflected upper surface 206 may exhibit a compressive stress state at least partially due to the mechanical deflection thereof. The PDC 200 further includes the region 220, as previously discussed, which is the space between the deflected bottom surface 208 of the mechanically-stressed PCD table 202, the inner lateral surface 214 of the substrate 204, and the inner surface 218 of the substrate 204. Alternatively, a compressible material (e.g., copper, brass, braze material, or bronze) may be placed between the mechanically-stressed PCD table 202 and the substrate 204 prior to bonding. In such a configuration, the compressible material may at least partially fill the region 220 after bonding. Optionally, the preformed PCD table may be at least partially supported by the compressible material during the HPHT bonding process. The mechanical deflection of the mechanically-stressed PCD table 202 may increase the toughness and strength of the PDC 200 and/or reduce vibrations in the PDC 200 during use. Further, the region 220 may redirect at least part of the cutting heat generated by the mechanically-stressed PCD table during use away from a central region of the substrate 204, effectively reducing heat damage to the substrate 204.

FIG. 3 is a cross-sectional view of an embodiment of a PDC 300 including a mechanically-stressed PCD table 302 that is partially leached and attached to only a portion of a substrate 304 due to a shape of the substrate 304 using a mechanical fastener 322. The mechanically-stressed PCD table 302 includes a deflected upper surface 306 spaced from a deflected bottom surface 308 that faces an interfacial surface 312 of the substrate 304. Thus, as illustrated, the deflected upper surface 306 and the deflected bottom surface 308 may exhibit a mechanical deflection. The substrate 304 may be formed from the same materials as the substrate 104.

In the illustrated embodiment, the mechanically-stressed PCD table 302 includes a first region 337 that extends inwardly from every surface of the mechanically-stressed PCD table 302. For example, the first region 337 may be at least partially leached to remove at least a portion (e.g., substantially all) of a catalyst material therefrom used in the initial formation of the mechanically-stressed PCD table 302. The mechanically-stressed PCD table 302 also includes a second unleached region 338 that is remote from every surface of the mechanically-stressed PCD table 302. For example, the first region 337 may be formed by immersing a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A) used to form the mechanically-stressed PCD table 302 in a leaching agent. The thickness of the first region 337 may be about 50 μm to about 500 μm, such as about 200 μm to about 400 μm, about 150 μm to about 300 μm, or greater than about 400 μm. In another embodiment, the mechanically-stressed PCD table 302 includes a first leached region that extends inwardly a distance from only some of the surfaces of the mechanically-stressed PCD table 302. For example, one or more surfaces of a preformed PCD table may be masked or otherwise covered while immersing the preformed PCD table in a leaching agent.

In the illustrated embodiment, the mechanically-stressed PCD table 302 further includes an inner peripheral surface 324 that defines an aperture therethrough (e.g., a through hole) that receives the mechanical fastener 322. The inner peripheral surface 324 of the mechanically-stressed PCD table 302 extends from the deflected upper surface 306 of the mechanically-stressed PCD table 302 to the deflected bottom surface 308 of the mechanically-stressed PCD table 302. In the illustrated embodiment, the inner peripheral surface 324 of the mechanically-stressed PCD table 302 is shown to be substantially planar and extends substantially perpendicularly between the deflected upper surface 306 and the deflected bottom surface 308 of the mechanically-stressed PCD table 302. However, the inner peripheral surface 324 of the mechanically-stressed PCD table 302 may exhibit a number of different orientations. For example, the inner peripheral surface 324 of the mechanically-stressed PCD table 302 may extend from the deflected upper surface 306 at an oblique angle (e.g., obtuse angle) relative to the deflected upper surface 306.

In the illustrated embodiment, the substrate 304 may be substantially similar to the substrate 204 shown in FIG. 2. For example, the substrate 304 may include an interfacial surface 312 that at least partially contacts the deflected bottom surface 308 of the mechanically-stressed PCD table 302. The substrate 304 may also include an inner lateral surface 314 and an inner surface 318 that, along with the deflected bottom surface 308, at least partially define a region 320 into which the mechanically-stressed PCD table 302 may deflect. In other embodiments, the substrate 304 may be substantially similar to any of the substrates disclosed herein. The substrate 304 may be formed from any of the substrate materials disclosed herein.

The substrate 304 further includes an inner peripheral surface 326 that defines an aperture that also receives the mechanical fastener 322. The aperture defined by the inner peripheral surface 326 of the substrate 304 may exhibit a shape that is substantially similar to or different than the aperture defined by the inner peripheral surface 324 of the mechanically-stressed PCD table 302.

The inner peripheral surface 326 of the substrate 304 may exhibit any number of orientations, shapes, or topographies. In the illustrated embodiment, the inner peripheral surface 326 of the substrate 304 extends from the inner surface 318 of the substrate 304 to a bottom surface 328 of the substrate 304. For example, the inner peripheral surface 326 of the substrate 304 may extend substantially perpendicularly from or at an oblique angle relative the inner surface 318. In another embodiment, the inner peripheral surface 326 of the substrate 304 may only extend from the inner surface 318 to an intermediate location within the substrate 304. In an embodiment, the inner peripheral surface 326 of the substrate 304 may be at least partially threaded so that the mechanical fastener 322 can threadly engage with it. In another embodiment, the inner peripheral surface 326 of the substrate 304 may be at least partially threaded and may only extend from the inner surface 318 to an intermediate location partially through the substrate 304. In another embodiment, the inner peripheral surface 326 may exhibit a shape configured to have the mechanical fastener 322 deformed, press-fitted, or otherwise coupled thereto such that the mechanical fastener 322 presses against the mechanically-stressed PCD table 302 in a controlled manner. For example, the mechanically-stressed PCD table 302 may be forced against the interfacial surface 312. More specifically, for example, the mechanically-stressed PCD table 302 may be forced against the interfacial surface 312 such that the mechanically-stressed PCD table exhibits a specific pre-load at a cutting edge.

The mechanical fastener 322 may include any type of mechanical fastener that is capable of applying a force to the deflected upper surface 306 of mechanically-stressed PCD table 302. Examples of suitable mechanical fasteners include, but not limited to, a clamp, a rivet, a pin, or a threaded shaft (e.g., a screw or a bolt).

In the illustrated embodiment, the mechanical fastener 322 may include a top portion 330, an at least partially threaded shaft 332, and an at least partially threaded nut 334 configured to threadly engage the at least partially threaded shaft 332. The top portion 330 of the mechanical fastener 322 is designed to apply a force to an upper surface of a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A) used to form the mechanically-stressed PCD table 302 in order to cause deflection in the preformed PCD table. Deflecting the preformed PCD table may apply a pre-load at a cutting edge and/or cutting portion of the mechanically-stressed PCD table 302. In the illustrated embodiment, the top portion 330 exhibits a generally semi-spherical shape. However, the top portion 330 may exhibit any suitable shape. The at least partially threaded shaft 332 may have a length sufficient to extend from the deflected upper surface 306 of the mechanically-stressed PCD table 302 through the bottom surface 328 of the substrate 304 so the at least partially threaded nut 334 may be threadly attached to the at least partially threaded shaft 332. In an embodiment, the mechanical fastener 322 may be configured, positioned, and/or exhibit a shape configured to protect one or more components (e.g., the top portion 330) of the mechanical fastener 322 from erosion and/or wear due to exposure to drilling fluid and/or cuttings. In another embodiment, one or more components of the mechanical fastener 322 may be coplanar or congruent with a cutting surface of the PDC 300. Any part of the mechanical fastener 322 may be formed from a metal, a ceramic, a polymer, a composite, a superhard material, another suitable material, or any combination of the above.

In an embodiment, a washer 336 may be placed between the top portion 330 of the mechanical fastener 322 and the deflected upper surface 306. The washer 336 may prevent the top portion 330 from contacting the deflected upper surface 306. In an embodiment, the washer 336 may comprise a compliant material, such as copper, aluminum, brass, bronze, alloys of any of the foregoing, or another suitable material. In another embodiment, the washer 336 may comprise a hard and/or wear resistant material (e.g., a superhard material, alumina, high-strength steel) or may be coated with a hard and/or wear resistant material.

In an embodiment, the washer 336 may be configured to more evenly distribute the pressure from the top portion 330 of the mechanical fastener 322 to the deflected upper surface 306 of the mechanically-stressed PCD table 302. For example, the washer 336 may exhibit a washer-to-PCD table interface that is controlled and/or selected to more uniformly distribute a force from the mechanical fastener 322 through the mechanically-stressed PCD table 302 than if the washer 336 is omitted. More uniformly distributing the force from the mechanical fastener 322 through the mechanically-stressed PCD table 302 may reduce the likelihood of fracture and maintain a high contact pressure throughout the washer-to-PCD table interface (e.g., a bottom surface of the washer 336 that contacts the deflected upper surface 306 of the mechanically-stressed PCD table 302 may exhibit a non-planar geometry). In another embodiment, the washer 336 may dampen vibrations in the PDC 300. For example, friction between the top portion 330, the washer 336, and the deflected upper surface 306 may dampen vibrations therebetween, thereby improving the life of the PDC 300. Any part of the mechanical fastener 322 may be formed from a metal, a ceramic, a polymer, a composite, another suitable material or any combination of the above. Further, the washer 336 and the top portion 330 of the mechanical fastener 322 may be configured such that neither washer 336 nor the top portion 330 is a cutting surface of the mechanically-stressed PCD table 302. Additionally, a secondary washer (not shown) may be placed between the at least partially threaded nut 334 and the bottom surface 328 of the substrate 304.

Techniques for mechanically coupling the PDC 300 to a drill bit body are disclosed in U.S. Pat. Nos. 7,533,739; 7,942,218; 8,079,431; 8,479,845; and 8,528,670. The disclosures of each of the foregoing patents are incorporated herein, in their entirety, by this reference. Any of the mechanical coupling structures and/or techniques disclosed in the foregoing patents or disclosed herein may be used in any of the PDC embodiments disclosed herein to mechanically couple the PDCs to a drill bit body.

The PDC 300 is formed by placing a bottom surface of a preformed PCD table, which may be initially substantially planar, adjacent to the interfacial surface 312 of the substrate 304. The at least partially threaded shaft 332 is inserted through the apertures defined by the inner peripheral surfaces 324 and 326. The at least partially threaded shaft 332 is inserted sufficiently to allow the top portion 330 of the mechanical fastener 322 to contact at least one of the upper surface of the preformed PCD table, the washer 336 (if present), or another surface (e.g., the inner peripheral surface 324) of the preformed PCD table. The at least partially threaded nut 334 is then attached to the at least partially threaded shaft 332. The at least partially threaded nut 334 is then rotated to tighten the mechanical fastener 322 such that the top portion 330 of the mechanical fastener applies a force to the upper surface or other surface of the preformed PCD table sufficient to deflect the preformed PCD table in a controlled manner toward the substrate 304 to form the mechanically-stressed PCD table 302 that is supported along an outer peripheral edge of the substrate 304. For example, the at least partially threaded nut 334 may be sufficiently rotated to cause the mechanically-stressed PCD table 302 to exhibit a specific pre-load at a cutting edge thereof.

In the illustrated embodiment, the at least partially threaded nut 334 may be controllably tighten sufficiently to deflect the preformed PCD table toward the substrate 304 such that the deflected bottom surface 308 of the mechanically-stressed PCD table 302 completely contacts the interfacial surface 312 of the substrate 304. In another embodiment, the at least partially threaded nut 334 may be controllably tightened such that the deflected bottom surface 308 of the mechanically-stressed PCD table 302 contacts only a portion of the interfacial surface 312 of the substrate 304. In another embodiment, the at least partially threaded nut 334 may be controllably tightened such that the deflected bottom surface 308 of the mechanically-stressed PCD table 302 partially contacts the inner surface 318 of the substrate 304. In an embodiment, a preformed PCD table exhibiting a diameter of 16 mm and a thickness of 0.080 inches may be mechanically-stressed using a threaded screw or bolt (e.g., a #10 screw or bolt) by applying a torque of about 40 inch pounds to the mechanical fastener 322 in order to deflect the preformed PCD table toward the substrate 304. In another embodiment, the torque applied to deflect the preformed PCD table toward the substrate 304 is less than or greater than about 1000 inch pounds (e.g., at least about 10 inch pounds, at least about 40 inch pounds, at least about 100 inch pounds, about 10 inch pounds to about 100 inch pounds, about 100 inch pounds to about 1000 inch pounds, about 1000 inch pounds to about 2000 inch pounds, about 2000 inch pounds to about 3000 inch pounds, or greater than about 3000 inch pounds).

Mechanically coupling the mechanically-stressed PCD table 302 to the substrate 304 allows the use of relatively thick PCD tables. A relatively thick PCD table may exhibit a thickness of about 0.120 inches or greater. For example, a relatively thick PCD table may have a thickness of about 0.120 inches to about 0.150 inch, about 0.150 inch to about 0.200 inch, about 0.200 inch to about 0.300 inches, about 0.300 inch to about 0.350 inch, about 0.350 inch to about 0.400 inch, greater than about 0.200 inch, or greater than 0.400 inch. Using relatively thick PCD tables may improve the life of the PDC. However, in other embodiments, the PCD table may have a thickness less than about 0.120 inch.

It is believed that the PDC 300 may exhibit improved toughness and/or improved strength, and may prevent or limit heat damage to the substrate 304 due to the space in the region 320. It also directs the cutting loads to the supported edge of the substrate 304, which may limit or prevent vibration of the PDC 300. For example, friction between the mechanically-stressed PCD table 302 and the interfacial surface 312 may dampen the vibrations of the PDC 300 during cutting operations. Additionally, the mechanically-stressed PCD table 302 that includes a second region 338 remote from the surface of the mechanically-stressed PCD table 302 that is substantially unleached may increase the strength of the PDC 300.

FIG. 4 is a cross-sectional view of a PDC 400 including a mechanically-stressed PCD table 402 attached to a substrate 404, with a washer 441 disposed therebetween. The mechanically-stressed PCD table 402 is attached to the substrate 404 using a mechanical fastener 422. The mechanically-stressed PCD table 402 is formed from a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A) that includes an upper surface spaced from a bottom surface. The bottom surface may be substantially planar and face an interfacial surface 412 of the substrate 404. The preformed PCD table may be mechanically-stressed via the mechanical fastener 422 to form the mechanically-stressed PCD table 402. The mechanically-stressed PCD table 402 further includes an inner peripheral surface 424 that defines an aperture that receives the mechanical fastener 422. The preformed PCD table may comprise, for example, an at least partially leached PCD table or other thermally-stable PCD table, and the substrate 404 may be formed from the same materials as the substrate 104.

The substrate 404 includes an interfacial surface 412 and an inner peripheral surface 426 that defines an aperture that receives the mechanical fastener 422. In the illustrated embodiment, the interfacial surface 412 extends radially inward from an outer lateral surface 416 of the substrate 404 to an upper edge of the inner peripheral surface 426 of the substrate 404. The interfacial surface 412 may exhibit any number of shapes and topographies. In the illustrated embodiment, the interfacial surface 412 of the substrate 404 is substantially planar. In another embodiment, the interfacial surface 412 of the substrate 404 may exhibit a concave or convex curvature.

The substrate 404 may also include a hole or aperture formed therein that may at least partially contain an at least partially threaded nut 434 when the at least partially threaded nut 434 is threadly coupled to the mechanical fastener 422. In the illustrated embodiment, the substrate 404 includes a bottom surface 428 that is opposite the interfacial surface 412 and extends for a distance from a bottom edge of the outer lateral surface 416 towards a center of the substrate 404. In the illustrated embodiment, the bottom surface 428 may be substantially planar. In another embodiment, the bottom surface 428 of the substrate 404 may exhibit any number to shapes and/or topographies. In the illustrated embodiment, the substrate 404 includes a second inner peripheral surface 439 extending from a radially innermost portion of the bottom surface 428 for a distance towards the interfacial surface 412. The distance that the second inner peripheral surface 439 extends from the bottom surface 428 may be less than, equal to, or greater than a thickness of the at least partially threaded nut 434 that it receives. The substrate 404 further includes an inner bottom surface 440 that extends between the inner peripheral surface 426 and the second inner peripheral surface 439. The second inner peripheral surface 439 and the inner bottom surface 440 may at least partially define a second aperture. The second aperture is generally larger than the aperture defined by the inner peripheral surface 426 of the substrate 404. The second aperture may have a minimum width (e.g., measured radially between the second inner peripheral surface 439) that is equal to or greater than the maximum width of the at least partially threaded nut 434. The substrate 404 defining a second aperture may be used in any of the mechanically-stressed PCD table embodiments disclosed herein.

As previously discussed, the PDC 400 includes a washer 441 disposed between the mechanically-stressed PCD table 402 and the substrate 404. The washer 441 includes an upper washer surface 442 that contacts the deflected bottom surface 408 of the mechanically-stressed PCD table 402 and a bottom washer surface 443 that contacts the interfacial surface 412 of the substrate 404. The washer 441 may also include an outer washer lateral surface 444 and an inner peripheral surface 445. In an embodiment, the outer washer lateral surface 444 of the washer 441 may be configured to exhibit the same lateral dimension and general shape as the substrate 404 (e.g., the outer lateral surface 416). In another embodiment, the outer washer lateral surface 444 may exhibit a diameter or lateral dimension that is different than the substrate 404. The inner peripheral surface 445 of the washer 441 may partially define an aperture (e.g., region 420) that receives the mechanical fastener 422. The aperture defined by the inner peripheral surface 445 of the washer 441 may or may not exhibit the same shape and size as at least one of the apertures defined by the inner peripheral surface 424 of the mechanically-stressed PCD table 402 and/or the aperture defined by the inner peripheral surface 426 of the substrate 404. Additionally, the surfaces of the washer 441 may exhibit any suitable topography. For example, the upper washer surface 442 may be curved to match the shape of the deflected bottom surface 408 of the mechanically-stressed PCD table 402 caused by the mechanical deflection of the deflected bottom surface 408. In another example, the bottom washer surface 443 may also be shaped to conform to the shape of the interfacial surface 412.

The washer 441 may be formed from a number of different materials. In an embodiment, the washer 441 is formed of a compliant material, such as a material that is less hard than the substrate 404 (e.g., cobalt-cemented tungsten carbide). For example, the washer 441 may comprise iron, nickel, copper, aluminum, alloys thereof, combinations thereof, or another suitable compliant material. In another embodiment, the washer 441 may be formed from a relatively hard material (e.g., a superhard material), such as a material that is at least as hard as the substrate 404. For example, the washer 441 may be made of polycrystalline diamond or cubic boron nitride. In another embodiment, the washer 441 may be made of the same material as the substrate 404, such as a cobalt-cemented tungsten carbide or any carbide material disclosed herein. In another embodiment, the washer 441 may be formed from a refractory metal, such as molybdenum, tantalum, vanadium, tungsten, niobium, alloys thereof, or combinations thereof. The washer 441 may be used in any of the embodiments disclosed herein.

The mechanical fastener 422 is substantially similar to or the same as the mechanical fastener 322 of FIG. 3. For example, the mechanical fastener 422 includes a top portion 430, an at least partially threaded shaft 432 configured to threadly engage the at least partially threaded nut 434 and an optional washer 436. The at least partially threaded shaft 432 of the mechanical fastener 422 may be configured such that the at least partially threaded shaft 432 does not extend past the bottom surface 428 of the substrate 404.

The PDC 400 is formed by placing the bottom surface of the preformed PCD table adjacent to the upper washer surface 442 and the interfacial surface 412 of the substrate 404 adjacent to the bottom washer surface 443. The at least partially threaded shaft 432 of the mechanical fastener 422 is inserted into the apertures defined by the inner peripheral surfaces 424, 426, 439, and 445. The at least partially threaded shaft 432 is inserted sufficiently so that the top portion 430 contacts the upper surface of the preformed PCD table or, optionally, contacts a washer 434. The at least partially threaded nut 434 is then threadly engaged with the at least partially threaded shaft 432. For example, the at least partially threaded nut 434 and the at least partially threaded shaft 432 are controllably rotated with respect to one another and the top portion 430 of the mechanical fastener 422 applies a force to the upper surface of the preformed PCD table. The at least partially threaded nut 436 or threaded shaft 432 is rotated sufficiently to deflect the preformed PCD table towards the substrate 404 to form the mechanically-stressed PCD table 402 having a deflected upper surface 406 exhibiting a compressive stress state at least partially due to the mechanical deflection thereof. For example, the preformed PCD table may deflect into the region 420 at least partially defined by the inner peripheral surface 445 of the washer 441.

In an embodiment, the substrate 404 may include a notch or recess configured designed to receive a portion of the washer 441. In another embodiment, the washer 441 may be brazed to the interfacial surface 412 prior to or after mounting the mechanically-stressed PCD table 402 to the substrate 404 using any of the braze methods disclosed herein. In another embodiment, the deflected bottom surface 408 of the mechanically-stressed PCD table 402 is brazed to the upper washer surface 442 before or after the mechanically-stressed PCD table 402 is mechanically-stressed. In another embodiment, a second mechanical washer (not shown) may be placed between the at least partially threaded nut 434 and the inner bottom surface 440 of the substrate 404.

FIG. 5 is a cross-sectional view of an embodiment of a PDC 500 including a mechanically-stressed PCD table 502 attached to a substrate 504, with a thin foil 546 disposed therebetween. The mechanically-stressed PCD table 502 and the substrate 504 are attached to each other using a mechanical fastener 522. Additionally, the PDC 500 is shown attached to a drill bit body 548 using the same mechanical fastener 522. For example, a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A) from which the mechanically-stressed PCD table 502 is formed may comprise an at least partially leached PCD table or other thermally-stable PCD table, and the substrate 504 may be formed from the same materials as the substrate 104.

Prior to deflecting the preformed PCD table to form the mechanically-stressed PCD table 502, the preformed PCD table includes an upper surface spaced from a bottom surface. The bottom surface may be substantially planar and face a concavely curved interfacial surface 512 of the substrate 504. The preformed PCD table also includes an inner peripheral surface 524 that defines an aperture that receives the mechanical fastener 522. The preformed PCD table may be manufactured according to any of the embodiments disclosed herein.

The interfacial surface 512 may be similar to any interfacial surfaces discussed herein. For example, in the illustrated embodiment, the interfacial surface 512 may exhibit a concave curvature, such as a generally spherical curvature. The substrate 504 includes an inner peripheral surface 526 defining an aperture that receives the mechanical fastener 522.

The mechanical fastener 522 may include a screw, a pin, a rivet, or a clamp. For example, a rivet may be swaged or plastically deformed into the structure. The mechanical fastener 522 may be substantially similar to the mechanical fastener 322 of FIG. 3. For example, the mechanical fastener 522 may include a top portion 530, an at least partially threaded shaft 532, an at least partially threaded nut 534 and an optional washer 536. The at least partially threaded shaft 532 of the mechanical fastener 522 may be configured such that the at least partially threaded shaft 532 does extend past a bottom surface 554 of the drill bit body 548.

The drill bit body 548 includes a recess 550 designed to receive the PDC 500. The drill bit body 548 may also include an inner peripheral surface 552 that defines an aperture that receives the mechanical fastener 522. In the illustrated embodiment, the at least partially threaded shaft 532 may be long enough to extend past a bottom surface 554 of the drill bit body 548. In another embodiment, the PDC 500 is attached to the drill bit body 548 in any suitable manner. For example, the PDC 500 may be attached to the drill bit body 548 by brazing, press fitting or by a retention member of the drill bit body 548.

The thin foil 546 is placed between the mechanically-stressed PCD table 502 and the substrate 504 such that the mechanically-stressed PCD table 502 compresses the thin foil 546 therebetween. The thin foil 546 may include an aperture designed to receive the at least partially threaded shaft 532 of the mechanical fastener 522. The thin foil 546 may be sufficiently thin that subsequent deflection and/or compression thereof does not result in significant loss of support for the mechanically-stressed PCD table 502. For example, the thin foil 546 may exhibit a thickness of about 0.00020 inches to about 0.0010 inches, such as about 0.0002 inches to about 0.0005 inches, about 0.0005 inches to about 0.0010 inches, about 0.0002 inches to about 0.005 inches, or about 0.0010 inches to about 0.0100 inches. In an embodiment, the thickness of the thin foil 546 may be substantially constant or varied.

The thin foil 546 may formed from a variety of different materials. In an embodiment, the thin foil 546 comprises a metal, such as copper, aluminum, iron, any suitable metal, combinations thereof, or alloys thereof. In another embodiment, the thin foil 546 is formed from a refractory metal, such as molybdenum, tantalum, vanadium, tungsten, niobium, alloys thereof, or combinations thereof. In another embodiment, the thin foil 546 is formed from a material that may increase friction between the mechanically-stressed PCD table 502 and the substrate 504. In another embodiment, the thin foil 546 may be formed from any material softer than the substrate 504 so as to distribute the pressure between the mechanically-stressed PCD table 502 and the substrate 504 more evenly. In another embodiment, the thin foil 546 is formed from of a material that provides improved heat transfer from the mechanically-stressed PCD table 502 to the substrate 504, such as a material that has a thermal conductivity of about 5 Btu/(hr ° F. ft) to about 225 Btu/(hr ° F. ft), about 15 Btu/(hr ° F. ft) to about 100 Btu/(hr ° F. ft), about 30 Btu/(hr ° F. ft) to about 75 Btu/(hr ° F. ft), or greater than about 75 Btu/(hr ° F. ft).

In another embodiment, the thin foil 546 may be replaced with a washer such that the washer is positioned between the performed PCD table and the interfacial surface 512 of the substrate 504. The washer may include any of the materials used for the thin foil 546. The washer may have a lateral thickness that is about equal to or less than the lateral thickness of the interfacial surface 512.

The PDC 500 is formed by placing the bottom surface of the preformed PCD table proximate to the interfacial surface 512, with the thin foil 546 positioned therebetween. The at least partially threaded shaft 532 of the mechanical fastener 522 is inserted into the aperture defined by the inner peripheral surfaces 524 and 526. The at least partially threaded shaft 532 is inserted sufficiently so that the top portion 530 is adjacent to the upper surface of the preformed PCD table or the optional washer 536. The at least partially threaded nut 534 is then attached to the bottom of the at least partially threaded shaft 532 and the at least partially threaded nut 534 is then rotated. The at least partially threaded nut 534 is torqued enough so that the force applied by the top portion 530 sufficiently deflects the preformed PCD table toward the substrate 504 to form the mechanically-stressed PCD table 502. The PCD material adjacent to the deflected upper surface 506 of the PCD table may exhibit a compressive stress state at least partially due to the mechanical deflection thereof

In embodiments shown in FIGS. 4 and 5 in which the washer 441 or thin foil 546 have relatively low thermal conductivities, the mechanically-stressed PCD table 502 is effectively thermally de-coupled from the substrate to which it is attached. For example, when the washer 441 or thin foil 546 are made from a refractory metal, the washer 441 or the thin foil 546 are considered to exhibit a relatively low thermal conductivity. For example, an increase in temperature in the mechanically-stressed PCD table during cutting operations may not generate significant thermal stresses in the PDC as a whole due to some limited compliance and/or slippage between the mechanically-stressed PCD table and the substrate. However, the mechanically-stressed PCD table 502 is at least partially thermally de-coupled regardless of the washer and/or thin foil material.

FIG. 6A is an exploded cross-sectional view of an embodiment of an assembly including a preformed PCD table 602 and a substrate 604. The preformed PCD table 602 includes an upper surface 606 spaced from a bottom surface 608 that faces an interfacial surface 612 of the substrate. For example, the preformed PCD table 602 may comprise an at least partially leached PCD table, another thermally-stable PCD table, or any suitable PCD table. The substrate 604 may be formed from the same materials as the substrate 104.

The bottom surface 608 of the preformed PCD table 602 may exhibit a pattern 656 thereon. The pattern may be formed on the bottom surface 608 after the preformed PCD table 602 has been sintered. For example, the pattern 656 may be formed on the bottom surface 608 using any suitable method including grinding, lapping, laser cutting, electro-discharge machining (“EDM”), or combinations thereof. Alternatively, the pattern 656 may be formed on the bottom surface 608 prior to or during sintering to form the preformed PCD table 602. For example, a mass of diamond particles may be pressed to form a green body. The green body may have the pattern 656 placed thereon using any suitable method including pressing (e.g., the mold used to form the green body includes a pattern that is transferred to the green body), lapping, grinding, machining, imprinting, or combinations thereof. Further, the pattern 656 may be formed on the bottom surface 608 during the HPHT process. For example, a mass of diamond powder may be placed into a cell assembly (e.g., a refractory metal canister) in which the cell assembly contains a pattern that is transferred to the mass of diamond particles during the HPHT sintering process. In an embodiment, the pattern 656 formed on the bottom surface 608 prior to or during sintering may be machined after sintering.

The interfacial surface 612 of the substrate 604 may exhibit a pattern 656 thereon that substantially corresponds to the pattern 656 on the preformed PCD table 602. The interfacial surface 612 of the substrate 604 may exhibit a depth d and a radius of curvature C. In the illustrated embodiment, the depth d and the radius of curvature C are measured from the upper most portions of the pattern 656. In another embodiment, the depth d and the radius of curvature C may be measured from the bottom most portion of the pattern 656. In another embodiment, the depth d and radius of curvature C may be measured as the average height of the interfacial surface 612 or any other suitable method. With reference to FIG. 6B, the depth d and the radius of curvature C may be selected so that a specific compressive stress and/or pressure distribution is generated in a deflected upper surface 606′ of the mechanically-stressed PCD table 602′, while not over stressing or fracturing the mechanically-stressed PCD table 602′. In an embodiment, only one of the bottom surface 608 or the interfacial surface 612 includes the pattern 656 formed thereon.

Generally, the pattern 656 may be designed to increase friction and attachment strength between the mechanically-stressed PCD table 602′ and the substrate 604. As such, the pattern 656 may exhibit any number of topographies. In the illustrated embodiment, the pattern 656 includes a series of peaks that form concentric circles about a central axis. Alternatively, the pattern 656 include ridges, grooves, steps, channels, recesses, sockets, slots, webs, matrixes, mesh, loops or any suitable pattern. The pattern 656 may or may not form concentric circles. In an embodiment, the pattern 656 on the interfacial surface 612 may exhibit a number of recesses that are randomly placed on the interfacial surface 612.

FIG. 6B is formed by placing the bottom surface 608 of the preformed PCD table 602 adjacent to the interfacial surface 612 of the substrate 604 and substantially aligning the preformed PCD table 602 and the substrate 604 such that the patterns 656 have respective geometries that substantially correspond to each other (e.g., there is no substantial space between the two or more patterned surfaces after deflecting the preformed PCD table 602). The preformed PCD table 602 and the substrate 604 are then placed into any pressure transmitting medium previously discussed herein and subjected to an HPHT process using any of the HPHT conditions disclosed herein. The HPHT process is sufficient to deflect the preformed PCD table 602 toward the substrate 604 and to attach the mechanically-stressed PCD table 602′ to the substrate 604. Deflecting and attaching the mechanically-stressed PCD table 602′ to the substrate 604 may generate a compressive stress state in the PCD material adjacent to the deflected upper surface 606′ of the mechanically-stressed PCD table 602′. Additionally, deflecting and attaching the mechanically-stressed PCD table 602′ to the substrate may cause the PCD material adjacent to the deflected bottom surface 608′ to exhibit a tensile stress state. In the illustrated embodiment, the deflected bottom surface 608′ fully contacts the interfacial surface 612 of the substrate 604. In another embodiment, the deflected bottom surface 608′ only partially contacts the interfacial surface 612 and forms a region between the deflected bottom surface 608′ and the interfacial surface 612.

As previously discussed with respect to other embodiments, in an embodiment, the mechanically-stressed PCD table 602′ is attached (e.g., bonded) to the substrate 604 by melting an infiltrant material from the substrate 604 during the HPHT process and infiltrating the infiltrant material into the interstitial regions of the mechanically-stressed PCD table 602′. For example, the infiltrant material may include cobalt from a cobalt-cemented tungsten carbide substrate. In another embodiment, the mechanically-stressed PCD table 602′ is attached to the substrate 604 by brazing or fastening with a mechanical fastener. After attaching the mechanically-stressed PCD table 602′ to the substrate 604, the mechanically-stressed PCD table 602′ may be leached to a selected leached depth from the deflected upper surface 606 and/or the at least one lateral surface, as previously described with respect to the PDC 100 of FIG. 1B.

It should be noted that the patterned 656 shown in FIGS. 6A and 6B may be employed in combination with any of the embodiments discussed herein using any of the patterns disclosed herein. For example, referring to FIG. 2, only a portion of the deflected bottom surface 208 and/or the interfacial surface 212 may have a pattern thereon. Referring to FIG. 3, at least one of the deflected bottom surface 308 and/or the interfacial surface 312 may have a pattern on at least a portion thereof. Referring to FIG. 4, at least one of the deflected bottom surface 408, the interfacial surface 412, the upper washer surface 442, or the bottom washer surface 443 may exhibit a pattern thereof. For example, in an embodiment, only a portion of the deflected bottom surface 408 may exhibit a pattern thereon. In another embodiment, both the deflected bottom surface 408 and the interfacial surface 412 may exhibit a pattern on the entirety of both surfaces. In another embodiment, only the upper and bottom washer surface 442, 443 may exhibit a pattern thereon. In another embodiment, the deflected bottom surface 408, the interfacial surface 412, the upper washer surface 442, and the bottom washer surface 443 may exhibit a pattern thereon. Referring to all embodiments disclosed herein, a foil may be placed between two or more surfaces where at least one surface exhibits a pattern thereon.

FIG. 7 is a cross-sectional view of an embodiment of a PDC 700 including a mechanically-stressed PCD table 702 that is attached to a substrate 704 using a mechanical fastener 722. For example, the mechanically-stressed PCD table 702 may be made from a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A). The preformed PCD table may be deflected and attached to the substrate 704 using a mechanical fastener 722.

The substrate 704 may include two or more regions that each exhibit different hardnesses. In the illustrated embodiment, the substrate 704 includes a relatively hard outer region 760 and a relatively softer inner region 758 that collectively form the substrate 704. Generally, the inner region 758 is formed from of a material that has a lower modulus of elasticity than the outer region 760. For example, the inner region 758 may be formed from a cobalt-cemented tungsten carbide having cobalt in an amount of about 15 weight % to about 20 weight % and the outer region 760 may be formed from cobalt-cemented tungsten carbide having cobalt in an amount of about 5 weight % to about 9 weight %. In another example, the inner region 758 may be formed from silicon carbide having a modulus of elasticity of about 300 GPa, while the outer region 760 may be formed from cobalt-cemented tungsten carbide having a modulus of elasticity of about 400 GPa. In another embodiment, the outer region 760 has a modulus of elasticity that is about 5% to about 50% higher than the inner region 758, such as a modulus of elasticity that is between about 5% to about 10% higher, about 10% to about 20% higher, about 20% to about 35% higher, and about 35% to about 50% higher. In another embodiment, the substrate 704 may include three or more regions, with each region exhibiting a different modulus of elasticity. The three of more regions may be arranged such that the region with the lower modulus of elasticity is positioned closer to a center of the substrate 704.

The substrate 704 further includes an interfacial surface 712 and an inner peripheral surface 726 defining an aperture that receives the mechanical fastener 722. For example, the interfacial surface 712 may be substantially planar because the deflection in the preformed PCD table to form the mechanically-stressed PCD table 702 is induced by the different elastic moduli of the inner and outer regions 758 and 760 of the substrate 704 and, in particular, the inner region 758 being more compliant than the outer region 760.

Prior to deflecting the preformed PCD table to form the mechanically-stressed PCD table 702, the preformed PCD table includes an upper surface spaced from a bottom surface and an inner peripheral surface 724 defining an aperture that receives the mechanical fastener 722. Additionally, the mechanical fastener 722 may be similar to the mechanical fastener 322 shown in FIG. 3.

The PDC 700 is formed by placing the bottom surface of the preformed PCD table adjacent to the interfacial surface 712 of the substrate 704. An at least partially threaded shaft 732 of the mechanical fastener 722 is inserted into the aperture defined by the inner peripheral surfaces 724 and 726. The at least partially threaded shaft 732 is inserted sufficiently such that a top portion 730 thereof contacts an upper surface of the preformed PCD table or, optionally, a washer 736 inserted therebetween. The at least partially threaded nut 734 is then attached to the bottom of the at least partially threaded shaft 732 and the at least partially threaded nut 734 is tighten. The at least partially threaded nut 734 and the at least partially threaded shaft 732 are tightened with respect to each other sufficiently to deflect the preformed PCD table toward the substrate 704. The mechanically-stressed PCD table 702 is predominately supported at an outer peripheral edge of the substrate 704.

FIG. 8 is a cross-sectional view of an embodiment of a PDC 800 including a plurality of stacked PCD tables, and a substrate 804, with the plurality of stacked PCD tables being attached to the substrate 804 using a mechanical fastener 822. In the illustrated embodiment, the plurality of stacked PCD tables includes a mechanically-stressed first PCD table 802 and a second PCD table 862. The first and second PCD tables 802, 862 may be formed from a first and second preformed PCD tables (e.g., the preformed PCD table 102 of FIG. 1A), respectively. The mechanically-stressed first PCD table 802 may include a deflected upper surface 806 spaced from a deflected bottom surface 808. The second PCD table 862 may include an upper surface 866 spaced from a bottom surface 868, both of which may or may not be deflected. Both the first and second PCD tables 802, 862 may include an inner peripheral surface 824, 864, respectively, that defines an aperture that receives a mechanical fastener.

In an embodiment, the first and second preformed PCD tables may have different properties, such as different wear resistance and/or thermal stability. For example, the first preformed table may comprise relatively smaller diamond grains, while the second preformed PCD table may comprise relatively larger diamond gains. In another embodiment, the first and second preformed PCD tables may have different interstitial materials occupying the interstitial regions thereof. For example, a metal-solvent catalyst may occupy at least a portion of the first preformed PCD table, while a carbonate catalyst may occupy at least a portion of the second preformed PCD table. Alternatively, the first preformed PCD table may be at least partially leached, while the second preformed PCD table may not be leached. In another embodiment, the first preformed PCD table may have been manufactured using a different HPHT sintering process than the second preformed PCD table. For example, the first preformed PCD table may be sintered at a higher temperature, a high pressure, with different constituents, with different diamond mixtures, for longer durations, or combinations thereof than the second preformed PCD table.

In the illustrated embodiment, the substrate 804 is substantially similar to the substrate 304 provided in FIG. 3 in that the substrate 804. For example, the substrate 804 may include an interfacial surface 812, an inner lateral surface 814, an inner surface 818 and an inner peripheral surface 826 that defines an aperture that receives the mechanical fastener. However, any of the other substrates disclosed herein may be used. The mechanical fastener 822 may also be similar to the mechanical fastener 322 in FIG. 3 in that the mechanical fastener 822 includes a top portion 830, a washer 836, an at least partially threaded shaft 832, and an at least partially threaded nut 834 that is configured to threadly engage with the at least partially threaded shaft 832. However, the mechanical fastener 822 may be configured as any of the mechanical fasteners described herein. Similarly, the washer 841 may be substantially similar to the washer 441 of FIG. 4. Though not shown, a thin foil may be provided and any of the surfaces may exhibit a pattern thereon.

In the illustrated embodiment, the PDC 800 may be formed by placing a bottom surface of the second preformed PCD table adjacent to the substrate 804. A bottom washer surface 843 of the washer 841 may then be placed adjacent to an upper surface of the second preformed PCD table. A bottom surface of the first preformed PCD table may then be placed adjacent to an upper washer surface 842 of the washer 841. The mechanical fastener 822 is then placed such that the at least partially threaded shaft 832 is positioned in the aperture defined by the inner peripheral surfaces 824, 864, 826. A washer 836 may be placed between the top portion 830 and the upper surface of the first preformed PCD table or, optionally, the washer 836 may be omitted. The at least partially threaded nut 834 is then threadly engaged with the at least partially threaded shaft 832 and tightened such that the top portion 830 applies a force to the upper surface of the first preformed PCD table to cause deflection of the mechanically-stressed first PCD table 802 toward the substrate 804. The mechanically-stressed first PCD table 802 may include PCD material near the deflected upper surface 806 that exhibits a compressive stress state due to the mechanical deflection thereof. In the illustrated embodiment, the at least partially threaded nut 834 is not tightened sufficiently to mechanically deflect the second PCD table 862. In other embodiment, the at least partially threated nut 834 is tightened sufficiently to mechanically deflect the second PCD table 862.

In an embodiment, the washer 841 may be omitted and the bottom surface of the first preformed PCD table may directly contact the upper surface of the second preformed PCD table. In such an embodiment, both the first preformed PCD table and the second preformed PCD table may be mechanically-stressed by tightening the mechanical fastener 822 to form the mechanically-stressed first and second PCD tables 802, 862. In another embodiment, the first and second PCD tables 802, 862 may be bonded together (e.g., directly or indirectly via the washer 841) using an HPHT process or by brazing before, during, or after the plurality of stacked PCD tables are deflected and/or attached to the substrate 804. In another embodiment, the first and second PCD tables 802, 862 may be bonded to the washer 841 using an HPHT process (e.g., where the washer 841 may include a cobalt-cemented tungsten carbide substrate) or by brazing before, during, or after the plurality of stacked PCD tables are attached to the substrate 804. In another embodiment, the plurality of stacked PCD tables may be bonded to the substrate using an HPHT process or by brazing such that the mechanical fastener 522 may be removed after the plurality of stacked PCD tables are bonded to the substrate 804. In another embodiment, at least one of the first PCD table 802 or the second PCD table 862 may exhibit a shape (e.g., a generally U-shape) that allows a portion of the deflected bottom surface 808 of the first PCD table 802 to directly contact a portion of the upper surface 866 of the second PCD table 862, while also allowing one or more regions to exist between the first and second PCD tables 802, 862 where there is no contact between the first and second PCD tables 802, 862 after the first and second PCD tables 802, 862 are deflected. For example, similar to the substrate 304 of FIG. 3, the first and/or second PCD tables 802, 862 may have an inner lateral surface and an inner surface. In another embodiment, three or more PCD tables may be used.

The mechanically-stressed PCD table 802 is predominately supported along its peripheral edge. Mechanically-stressed PCD tables that are predominately supported along their peripheral edge may reduce cutting “chatter” due to compliance.

FIG. 9 is a cross-sectional view of an embodiment of a PDC 900 including a mechanically-stressed PCD table 902, a substrate 904, and a braze layer 970 therebetween that bonds the mechanically-stressed PCD table 902 to the substrate 904. For example, the mechanically-stressed PCD table 902 may be formed from a preformed PCD table (e.g., the preformed PCD table 102 of FIG. 1A). The preformed PCD table may be bonded to the substrate 904 using a braze layer 970 disposed therebetween. In an embodiment, the preformed PCD table may be deflected when the preformed PCD table is brazed to the substrate 904.

In the illustrated embodiment, the substrate 904 is substantially similar to the substrate 104 shown in FIGS. 1A and 1B. For example, the substrate 904 exhibits a generally continuous concave curved interfacial surface 912. In other embodiments, the substrate 904 may be substantially similar to any of the other substrates disclosed herein. The substrate 904 may be formed from any of the substrate materials disclosed herein.

The braze layer 970 that bonds the mechanically-stressed PCD table 902 to the substrate 904 may be formed from one or more braze alloys. For example, the one or more braze alloys may comprise gold, silver, copper, or titanium alloys. For example, the one or more braze alloys may include gold-tantalum alloys or silver-copper-titanium alloys. In one specific embodiment, a braze alloy may comprise an alloy of about 4.5 weight % titanium, about 26.7 weight % copper, and about 68.8 weight % silver, otherwise known as TICUSIL®, which is currently commercially available from Wesgo Metals, Hayward, Calif.. In a further embodiment, a braze alloy may comprise an alloy of about 25 weight % gold, about 37 weight % copper, about 11 weight % nickel, about 15 weight % palladium, and about 13 weight % manganese, otherwise known as PALNICUROM® 11, which is also currently commercially available from Wesgo Metals, Hayward, CA. Another suitable braze alloy may include about 92.3 weight % nickel, about 3.2 weight % boron, and about 4.5 weight % silicon. Yet another suitable braze alloy may include about 92.8 weight % nickel, about 1.6 weight % boron, and about 5.6 weight % silicon. In another suitable braze alloy may include cobalt, nickel, iron, another Group VIII metal, alloys thereof, or combinations thereof. Additional examples of suitable braze alloys are disclosed in U.S. Pat. No. 8,236,074, the disclosure of which is incorporated herein, in its entirety, by this reference.

In an embodiment, the PDC 900 may be formed by placing the preformed PCD table at least proximate to the interfacial surface 912 with one or more braze alloys therebetween to form an assembly. The assembly is then placed in a pressure transmitting medium to form a cell assembly. The cell assembly is then subjected to an HPHT process. The pressure and temperature of the HPHT process may be sufficient to deflect the preformed PCD table toward the substrate 904 such that a deflected bottom surface 908 the mechanically-stressed PCD table 902 at least partially contacts the interfacial surface 912 and is attached to the substrate 904. For example, the mechanically-stressed PCD table 902 bonds to the interfacial surface 912 upon cooling via the braze layer 970.

In an embodiment, the pressure and temperature of the HPHT process may fall within a diamond-stable region of the carbon equilibrium pressure-temperature phase diagram. For example, the HPHT process may exhibit a pressure in the pressure transmitting medium of at least about 2 GPa (e.g., at least about 6 GPa, at least about 7.5 GPa, or at least about 9.0 GPa) and a temperature of at least about 800° C., (e.g., at least about 1100° C., at least about 1350° C., or about 1200° C. to about 1450° C.). In an embodiment, the temperature may be selected to at least partially melt at least some of the one or more braze alloys to form the braze layer 970. For example, if the braze material is TICUSIL®, the temperature of the HPHT process may be at least about 900° C. In another example, if the one or more braze alloys includes PALNICUROM® 11, the temperature of the HPHT process may be at least about 1113° C. In another embodiment, the braze layer 970 may be omitted and a cementing constituent (e.g., cobalt) from the substrate may at least partially infiltrate the preformed PCD table and bond it to the substrate.

The resulting PDC 900 includes the mechanically-stressed PCD table 902 bonded to the substrate 904. PCD material at and/or near a deflected upper surface 906 of the mechanically-stressed PCD table 902 may exhibit a compressive stress state at least partially due to the mechanical deflection thereof. Similarly, PCD material at and/or near the deflected bottom surface 908 of the mechanically-stressed PCD table 902 may exhibit a tensile stress state at least partially due to the mechanical deflection thereof. Deflecting the preformed PCD table to form the mechanically-stressed PCD table 902 may increase the toughness and strength of the PDC 900 and/or reduce vibration damage in the PDC 900 during use.

In other embodiments, the preformed PCD table may be deflected before or after the preformed PCD table or a mechanically-stressed PCD table is bonded to a substrate. For example, a preformed PCD table may be positioned adjacent to a substrate having a concavely curved interfacial surface. The preformed PCD table may then be deflected and attached to a substrate using a mechanical fastener according to any of the methods disclosed herein (e.g., the methods described in FIG. 3-5, 7, or 8) to form an assembly including a mechanically-stressed PCD table attached to a substrate. In an embodiment, the one or more braze alloys may be disposed between one or more components of the assembly (e.g., the deflected bottom surface 308 of the mechanically-stressed PCD table 302 and the interfacial surface 312 of the substrate 304 of FIG. 3). The assembly may then be heated in a vacuum furnace or an HPHT process to at least partially melt the one or more braze alloys. The mechanically-stressed PCD table bonds to the interfacial surface of the substrate upon cooling via a braze layer to form a PDC. In another embodiment, the braze layer 970 may be omitted and a cementing constituent (e.g., cobalt) from the substrate may at least partially infiltrate the preformed PCD table and bond it to the substrate. The mechanical fastener may be removed from the PDC after the PDC is formed or the mechanical fastener may remain. In another example, a preformed PCD table may be bonded to a substrate via one or more braze alloys or infiltrants (e.g., Group VIII metals, such as cobalt, nickel, iron, or alloys thereof), for example, in a manner that does not substantially deflect the preformed PCD table. The preformed PCD table bonded to the interfacial surface of the substrate may then be deflected using a mechanical fastener.

FIG. 10 is a cross-sectional view of a PDC 1000 including plurality of stacked PCD tables 1072 that are attached to a substrate 1004 and bonded together. The plurality of stacked PCD tables 1072 may include, for example, a first, second, and third PCD tables 1002, 1062, 1074 that are bonded together. At least one (e.g., all) of the first, second, or third PCD tables 1002, 1062, 1074 may be mechanically-stressed. Each of the first, second, and third PCD tables 1002, 1062, 1074 may include upper surfaces 1006, 1066, 1076 (e.g., deflected upper surface) spaced from respective bottom surfaces 1008, 1068, 1078 (e.g., deflected bottom surface), which each exhibit a mechanical deflection. The substrate 1004 may be substantially similar to any of the substrates disclosed herein and may be formed from the same materials as substrate 104. For example, the substrate 1004 may be substantially similar to the substrate 104 of FIG. 1.

The plurality of stacked PCD tables 1072 may be formed from a plurality of preformed PCD tables (e.g., the preformed PCD table 102 of FIG. 1A). In the illustrated embodiment, the first, second, and third PCD tables 1002, 1062, 1074 may be formed from a first, second, and third preformed PCD tables. In an embodiment, at least one of the first, second, or third preformed PCD tables may include a substantially planar bottom surface. In an embodiment, similar to the first and second PCD tables 802, 862 of FIG. 8, at least some of the plurality of preformed PCD tables may exhibit different wear resistances, different thermal stability characteristics, or other physical properties that are different. In an embodiment, each of the plurality preformed PCD tables may include an inner peripheral surface defining an aperture that receives a mechanical fastener therein that clamps the plurality of stacked PCD tables 1072 to the substrate 1004. In an embodiment, each of the plurality preformed PCD tables may be partially or substantially completely leached preformed PCD tables as disclosed herein. In an embodiment, at least some of the preformed PCD tables may include patterns formed on one or more surfaces thereof In an embodiment, at least two of the plurality of stacked PCD tables 1072 may include a washer (e.g., the washer 841 of FIG. 8) positioned therebetween. In such an embodiment, at least one of the at least two of the plurality of stacked PCD tables 1072 may be brazed to the washer. The washer may prevent or limit at least one of the PCD tables that form the plurality of stacked PCD tables 1072 from being mechanically-stressed. In an embodiment, at least some of the bonding layers 1070 may be different from each other (e.g., exhibit different compositions, exhibit different thickness, etc.).

The PDC 1000 may be formed by placing a bottom surface of the first preformed PCD table adjacent to an upper surface of the second preformed PCD table, the bottom surface of the second preformed PCD table adjacent to an upper surface of the third preformed PCD table, and the bottom surface of the preformed PCD table adjacent to an interfacial surface 1012 of the substrate 1004 to form an assembly. Any of the one or more braze alloys and/or infiltrants disclosed herein may be disposed between at least one (e.g., each) of the first preformed PCD table and the second preformed PCD table, the second preformed PCD table and the third preformed PCD table, or the third preformed PCD table and the interfacial surface. In an embodiment, the assembly may be placed in a pressure transmitting medium and subjected to an HPHT process that is substantially similar to the HPHT process of FIG. 9. For example, the HPHT process may exhibit a pressure sufficient to deflect at least one (e.g., all) of the first, second, and third preformed PCD tables to form at least one of the first, second, or third mechanically-stressed PCD tables 1002, 1062, 1074. The HPHT process may also exhibit a temperature sufficient to at least partially melt the one or more braze alloys and/or infiltrants thereby bonding at least some of the PCD tables 1002, 1062, 1074 together and/or the plurality of stacked PCD tables 1072 to the substrate 1004 via bonding layers 1070.

In another embodiment, the PDC 1000 may be formed using first, second, and third preformed PCD tables and the substrate 1004 that each include an inner peripheral surface (not shown). Each inner peripheral surface may define an aperture that receives a mechanical fastener (not shown). The PDC 1000 may be formed by placing a bottom surface of the first preformed PCD table adjacent to an upper surface of the second preformed PCD table, the bottom surface of the second preformed PCD table adjacent to an upper surface of the third preformed PCD table, and the bottom surface of the preformed PCD table adjacent to an interfacial surface 1012 of the substrate 1004 to form an assembly. Any of the one or more braze alloys and/or infiltrants disclosed herein may be disposed between at least one of the first preformed PCD table and the second preformed PCD table, the second preformed PCD table and the third preformed PCD table, or the third preformed PCD table and the interfacial surface. A mechanical fastener may then be positioned through the apertures. The mechanical fastener may be used to deflect at least one (e.g., all) of the first, second, or third preformed PCD tables and attach the plurality of stacked PCD tables 1072 to the substrate using any of the methods disclosed herein. Before, after, or during deflection of at least one of the first, second, or third, preformed PCD tables using the mechanical fastener, at least one of the plurality of stacked PCD tables 1072, the mechanical fastener, or the substrate 1004 may be heated to at least partially melt the one or more braze alloys and/or infiltrants. For example, the plurality of stacked PCD tables 1072, the mechanical fastener, and the substrate 1004 may be heated in a vacuum furnace or an HPHT process. In an embodiment, after the one or more braze alloys and/or infiltrants are at least partially melted, the mechanical fastener may be removed from the PDC 1000.

The resulting PDC 1000 includes a plurality of stacked PCD tables 1072 (e.g., the first, second, and third PCD tables 1002, 1062, 11074) that are bonded to together and attached to the substrate 1004. PCD material at and/or near each deflected upper surface of the plurality of stacked PCD tables 1072 may exhibit a compressive stress state at least partially due to the mechanical deflection thereof. Similarly, PCD material at and/or near a deflected bottom surface of the plurality of stacked PCD tables 1072 may exhibit a tensile stress state at least partially due to the mechanical deflection thereof. Deflecting at least one of the first, second, or third mechanically-stressed PCD tables 1002, 1062, 1074 may increase the toughness and strength and/or reduce vibrations of the PDC 1000 during use.

FIG. 11 is a cross-sectional view a plurality of stacked PCD tables 1172 that are bonded together and are not attached to a substrate. In the illustrated embodiment, the plurality of stacked PCD tables 1172 includes a first, second, and third PCD tables 1102, 1162, 1174 bonded together. At least one (e.g., all) of the first, second, and third PCD tables 1102, 11062, 1174 may be mechanically-stressed.

The first, second, and third PCD tables 1102, 1162, 1174 may be formed from a first, second, and third preformed PCD tables (e.g., the preformed PCD table 102 of FIG. 1A), respectively. At least one of the first, second, and third PCD tables 1102, 1162, and 1174 may exhibit different physical properties, such as different wear resistances and/or thermal stability characteristics. In another embodiment, the plurality of stacked PCD tables 1172 may include two stacked PCD tables bonded together or four or more PCD tables bonded together. In another embodiment, the plurality of stacked PCD tables 1172 may include an inner peripheral surface defining an aperture therein that receives a mechanical fastener. In another embodiment, at least some of the plurality of stacked PCD tables 1172 may include a pattern formed on one or more surfaces thereof In another embodiment, at least one optional washer (e.g., washer 841 of FIG. 8) may be positioned between two or more of the plurality of preformed PCD tables before the plurality of preformed PCD tables are deflected. In such an embodiment, the at least one optional washer may prevent one or more of the plurality of stacked PCD tables 1172 from being deflected. In the illustrated embodiment, at least some of the braze layers 1170 may be different from each other (e.g., exhibit different compositions, exhibit different thickness, etc.).

In an embodiment, the plurality of stacked PCD tables 1172 may be formed by placing a bottom surface of the first preformed PCD table proximate to an upper surface of the second preformed PCD table and placing a bottom surface of the second preformed PCD table proximate to an upper surface of the third preformed PCD table to form an assembly. Any of the one or more braze and/or infiltrant materials disclosed herein may be disposed between each of the preformed PCD tables. The assembly may then be placed into a pressure transmitting medium and heated in an HPHT process. For example, the HPHT process may apply a non-uniform force configured to deflect the first, second, and third preformed PCD tables. The HPHT process may also be configured to at least partially melt the one or more braze and/or infiltrant materials to bond the plurality of stacked PCD tables 1172 together.

In another embodiment, the plurality of stacked PCD tables 1172 may initially be formed using a substrate. For example, an assembly may be formed by placing a plurality of preformed PCD tables adjacent to each other with one or more braze and/or infiltrant materials disposed therebetween. The plurality of preformed PCD tables may then be placed adjacent to an interfacial surface of a substrate to form an assembly. In an embodiment, each of the plurality of preformed PCD tables includes an inner peripheral surface that defines an aperture that receives a mechanical fastener. The mechanical fastener may be used to attach the plurality of preformed PCD tables to the substrate while deflecting at least one (e.g., each) of the plurality of preformed PCD tables to form the plurality of stacked PCD tables 1172. At least one the plurality of stacked PCD tables 1172 are then heated to at least partially melt the one or more braze alloys thereby bonding the plurality of stacked PCD tables 1172 together. In the case of an infiltrant material, the PD tables may contact one another after the infiltrant material melts and infiltrates one or both PCD tables. In another embodiment, the assembly may be placed in a pressure transmitting medium and subject to an HPHT process configured to deflect the plurality of preformed PCD tables and at least partially melt the one or more braze and/or infiltrant materials to form the plurality of stacked PCD tables 1172 bonded together. In either embodiment, after the plurality of stacked PCD tables 1172 are bonded together, the substrate may be removed from the plurality of stacked PCD tables 1172. For example, substrate may be removed from the plurality of stacked PCD tables 1172 by removing the mechanical fastener therefrom. In another example, the substrate may be removed from the plurality of stacked PCD tables 1172 using a machining process, such as grinding, electro-discharge machining, lapping, using lasers, etc.

In an embodiment, the plurality of stacked PCD tables 1172 may then be attached to another surface after the plurality of stacked PCD tables 1172 are bonded together. The another surface may include a substrate, a drill bit body (e.g., drill bit body 548 of FIG. 5), or any other suitable surface. In an embodiment, the plurality of stacked PCD tables 1172 may be attached to the another surface by brazing, press-fitting, using a mechanical fastener, HPHT bonding (e.g., infiltrating one or more infiltrant materials into the interstitial regions of the plurality of stacked PCD tables 1172), or any other suitable technique. In an embodiment, the another surface may exhibit a curvature that substantially conforms to a curvature of a surface of the plurality of stacked PCD tables 1172. In another embodiment, one or more surfaces of the plurality of stacked PCD tables 1172 may be planarized using any suitable technique and then attached to a substantially planar surface. In such an example, the planarized surface of the plurality of stacked PCD tables 1172 may not exhibit a compressive or tensile stress state at and/or near the planarized surface.

The resulting plurality of stacked PCD tables 1172 includes at least one (e.g. only) mechanically-stressed PCD table that are bonded to together without using a substrate. PCD material at and/or near a deflected upper surfaces of the plurality of stacked PCD tables 1172 may exhibit a compressive stress state due to the mechanical deflection thereof Similarly, PCD material at and/or near a deflected bottom surface of the plurality of stacked PCD tables 1172 may exhibit a tensile stress state at least partially due to the mechanical deflection thereof. Deflecting at least one of the plurality of stacked PCD tables 1172 may increase the toughness and strength and/or reduce vibrations in the plurality of stacked PCD tables 1172 during use.

FIG. 12 is a schematic illustration of an embodiment of a method for fabricating a PDC 1200 including a PCD table that may be used as a preformed PCD table in any of the PDC embodiments disclosed herein. Referring to FIG. 12, a mass of diamond particles 1202 is positioned adjacent to a substrate 1204. The mass of diamond particles 1202 may exhibit a range of particle sizes and distributions. The mass of diamond particles 1202 may exhibit an average particle size about 0.1 μm to about 150 μm. In some embodiments, the mass of diamond particles 1202 may exhibit an average particle size of about 50 μm or less, such as about 30 μm or less or about 20 μm or less. In another embodiment, the average particle size of the mass of diamond particles 1202 may be about 10 μm to about 20 μm and, in some embodiments, about 15 μm to about 20 μm. The diamond particle size distribution of the mass of diamond particles may exhibit a single mode, or a bimodal or greater grain size distribution.

In an embodiment, the mass of diamond particles 1202 may be comprised of particles exhibiting a relatively larger size and at least one relatively smaller size. As used herein, the phrases “relatively larger” and “relatively smaller” refer to particle sizes (by any suitable method) that differ by at least a factor of two (e.g., 30 μm and 15 μm). According to various embodiments, the mass of diamond particles 1202 may include a portion exhibiting a relatively larger size (e.g., 30 μm, 20 μm, 15 μm, 12 μm, 10 μm, 8 μm) and another portion exhibiting at least one relatively smaller size (e.g., 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, less than 0.5 μm, less than 0.1 μm). In one embodiment, the mass of diamond particles 1202 may include a portion exhibiting a relatively larger size between about 10 μm and about 40 μm and another portion exhibiting a relatively smaller size between about 1 μm and 4 μm. In some embodiments, the mass of diamond particles 1202 may comprise three or more different sizes (e.g., one relatively larger size and two or more relatively smaller sizes), without limitation.

The mass of diamond particles 1202 may include one or more secondary materials that are not diamond particles. For example, in an embodiment, the mass of diamond particles 1202 may include a small amount of graphite, fullerenes, or another suitable non-diamond carbon material. For example, the mass of diamond particles 1202 may comprise 20 weight % or less (e.g., less than 10 weight %, less than 7.5 weight %, less than 5 weight %, between 10 weight % and 5 weight %, an amount greater than zero) of any of the non-diamond carbon materials disclosed herein. In another embodiment, the mass of diamond particles 1202 may include a small percentage of catalyst including at least one metal-solvent catalyst (e.g., cobalt, iron, nickel or alloys thereof), at least one alkali metal carbonate catalyst (e.g., one or more carbonates of Li, Na, and K), at least one alkaline earth metal carbonates (e.g., one or more carbonates of Be, Mg, Ca, Sr, and Ba), or any combination thereof. The catalyst may be present in an amount less than about 7.5 weight % of the mass of diamond particles 1202.

The mass of diamond particles 1202 may be pressed into a green body either prior to or after being positioned adjacent to the substrate 1204. The green body may be machined. For example, the green body may have a chamfer machined therein. In an embodiment, the green body may be shaped to form a disk that has substantially the same thickness throughout. In another example, the thickness of the green body may vary depending on the location. In another embodiment, the green body may be a generally rectangular body, a cylinder having a generally oval-shaped top surface, a generally wedge-shaped body, or any other suitable shaped body. Alternatively, the mass of diamond particles 1202 may not be pressed into a green state.

A substrate 1204 is provided to assist in sintering the mass of diamond particles 1202 during the HPHT sintering process. The substrate 1204 has an interfacial surface 1206. As shown in FIG. 12, the interfacial surface 1206 may exhibit a substantially planar topography. In some embodiments, the interfacial surface 1206 may exhibit topography that is not substantially planar. For example, the interfacial surface 1206 may exhibit a convex or concave curvature, a pattern formed thereon, or combinations thereof. For example, the interfacial surface 1206 may exhibit a pattern thereon, such as a grooved or ridged pattern as shown in FIG. 6.

The substrate 1204 may exhibit a wide range of shapes. For example, FIG. 12 shows the substrate 1204 exhibiting a cylindrical shape. Alternatively, the substrate 1204 may include a rectangular body, a cylinder having a generally oval shaped top surface, a generally wedge shaped body or any other suitable shaped body. The interfacial surface 1206 may be any surface of the substrate 1204 that is chosen. In FIG. 12, the interfacial surface 1206 was chosen to be the flat circular surface of the cylinder.

The substrate 1204 may be manufactured using a variety of materials. For example, the substrate 1206 may include, without limitation, cemented carbides, such as tungsten carbide, titanium carbide, chromium carbide, niobium carbide, tantalum carbide, vanadium carbide or combinations thereof. The cemented carbides may be cemented with iron, nickel, cobalt, other metals or alloys thereof. In an embodiment, the substrate 1204 may be a cobalt-cemented tungsten carbide substrate having an amount less than 20 weight % cobalt (e.g., less than 10 weight %).

The mass of diamond particles 1202 are placed adjacent to the interfacial surface 1206 of the substrate 1204 prior to the HPHT sintering process. The mass of diamond particles 1202 and the substrate 1204 may be enclosed in a pressure transmitting medium in order to efficiently sinter the mass of diamond particles. The pressure transmitting medium may be composed of a refractory metal can, graphite structure, pyrophyllite, and/or other suitable pressure transmitting structure to form a cell assembly. Examples of suitable gasket materials and cell structures for use in manufacturing PCD are disclosed in U.S. Pat. Nos. 6,338,754 and 8,236,074, each of which is incorporated herein, in its entirety, by this reference. Another example of a suitable pressure transmitting material is pyrophyllite, which is commercially available from Wonderstone Ltd. of South Africa.

The cell assembly, including the pressure transmitting medium and mass of diamond particles 1202 and substrate 1204 positioned therein, is subjected to an HPHT sintering process using an ultra-high pressure press at a temperature of at least about 1000° C., a pressure of at least about 5 GPa and a duration sufficient to bond the diamond particles together. In one embodiment, the temperature during the HPHT sintering process is about 1100° C. to about 2200° C. In another embodiment, the temperature during the HPHT sintering process is about 1200° C. to about 1450° C. (e.g., about 1300° C. to about 1400° C.). In an embodiment, the pressure during the HPHT sintering process is between 5.5 GPa to at least about 15 GPa. For example, the pressure in the pressure transmitting medium employed in the HPHT sintering process may be at least about 7.5 GPa (e.g., at least about 9.0 GPa, at least about 10.0 GPa, at least about 11.0 GPa, at least about 12.0 GPa or at least about 14.0 GPa), between about 8.0 GPa to about 14.0 GPa or between about 7.5 GPa to about 12.0 GPa.

The pressure values employed during the HPHT sintering processes or any of the HPHT processes disclosed herein refer to the pressure in the pressure transmitting medium at room temperature (e.g., about 25° C.) with application of pressure using an ultra-high pressure press and not the pressure applied to exterior of the cell assembly. The actual pressure in the pressure transmitting medium at sintering temperature may be slightly higher. The ultra-high pressure press may be calibrated at room temperature by embedding at least one calibration material that changes structure at a known pressure, such a PbTe, thallium, barium, or bismuth in the pressure transmitting medium. Further, optionally, a change in resistance may be measured across the at least one calibration material due to a phase change thereof. For example, PbTe exhibits a phase change at room temperature at about 6.0 GPa and bismuth exhibits a phase change at room temperature at about 7.7 GPA. Examples of suitable pressure calibration techniques are disclosed in G. Rousse, S. Klotz, A. M. Saitta, J. Rodriguez-Carvajal, M. I. McMahon, B. Couzinet, and M. Mezouar, “Structure of the Intermediate Phase of PbTe at High Pressure,” Physical Review B: Condensed Matter and Materials Physics, 71, 224116 (2005) and D. L. Decker, W.A. Bassett, L. Merrill, H. T. Hall, and J. D. Barnett, “High-Pressure Calibration: A Critical Review,” J. Phys. Chem. Ref. Data, 1, 3 (1972).

During the HPHT sintering process, the diamond particles form diamond-to-diamond bonding (e.g., sp³ bonding) therebetween to form a PCD table 1208 including a plurality of diamond grains exhibiting diamond-to-diamond bonding therebetween. The diamond grains define a plurality of interstitial regions therebetween, with at least a portion of the plurality of interstitial regions including an infiltrant material therein. The infiltrant material may comprise a catalyst material (e.g., a metal-solvent catalyst or a carbonate catalyst), graphite, fullerenes or combinations thereof.

The infiltrant material may enter the plurality of interstitial regions of the PCD table 1208 from a variety of sources. In an embodiment, the substrate 1204 comprises tungsten carbide that is cemented with a metal-solvent catalyst (e.g., cobalt, iron, nickel or alloys thereof). During the HPHT sintering process, the metal-solvent catalyst melts and infiltrates into the mass of diamond particles 1202 and occupies at least a portion of the plurality of interstitial regions of the PCD table 1208 so formed. The metal-solvent catalyst from the substrate 1204 may help bond the PCD table 1208 to the substrate 1204 by infiltrating at least a portion of the plurality of interstitial regions of the PCD table 1208. In another embodiment, the mass of diamond particles 1202 includes a carbonate catalyst material (e.g., alkali metal carbonates or alkaline earth metal carbonates) or a metal-solvent catalyst, and optionally graphite. During the HPHT sintering process, the carbonate catalyst melts and occupies at least a portion of the plurality of interstitial regions. In another embodiment, a disk containing the infiltrant material may be placed adjacent to the mass of diamond particles 1202. During the HPHT sintering process, the infiltrant material from the disk may infiltrate the mass of diamond particles 1202 and occupy at least a portion of the plurality of interstitial regions of the PCD table 1208 so formed.

Diamond-to-diamond bonding between the diamond particles 1202 is formed during the HPHT sintering process. The presence of a catalyst (e.g., cobalt, nickel, iron, an alloy of any of the preceding metals, an alkali metal carbonate, an alkaline earth metal carbonate or combinations thereof) facilitates intergrowth between the mass of diamond particles 1202 during the HPHT sintering process. Diamond may nucleate and grow from carbon provided by dissolved carbon in the catalyst provided, partially graphitized diamond particles, carbon from the substrate 1204, carbon from another source (e.g., graphite particles and/or fullerenes mixed with the diamond particles), or combinations of the foregoing.

The amount of catalyst material that occupies the plurality of interstitial regions may be present in the PCD table 1208 in an amount greater than zero and less than about 7.5 weight %. In some embodiments, the catalyst may be present in the PCD table 1208 in an amount of about 3 weight % to about 7 weight %, such as about 3 weight % to about 6 weight % (e.g., about 3 weight % to about 5 weight % or about 3 weight % to about 4 weight %). In other embodiments, the catalyst content may be present in the PCD table 1208 in an amount less than about 3 weight % such as about 1 weight % to about 3 weight % or a residual amount to about 1 weight %.

The PCD table 1208 may be separated from the substrate 1204 to form a preformed PCD table. The preformed PCD table may be formed by separating the PCD table 1208 from the substrate 1204 using grinding, lapping, laser cutting, electrical discharge machining (“EDM”), combinations thereof or other suitable methods.

In another embodiment, a preformed PCD table may be formed without the use of the substrate 1204. A mass of diamond particles having any of the above-mentioned average particle sizes, compositions, and distributions may be mixed with a small amount of catalyst material. For example the amount of catalyst material present in the mass of diamond particles may be less than about 7.5 weight %. The mass of diamond particles is then positioned in a pressure transmitting medium like any of the previously discussed pressure transmitting mediums. The cell assembly is then subjected to the HPHT sintering process using any of the HPHT conditions disclosed herein. The presence of a catalyst facilitates intergrowth between the mass of diamond particles during the HPHT sintering process to form a PCD table comprising bonded diamond grains defining a plurality of interstitial regions having the catalyst disposed within at least a portion of the plurality of interstitial regions.

In another embodiment, a preformed PCD table may be formed by placing a disk containing the catalyst material (e.g., metal-solvent catalyst or a carbonate catalyst) adjacent to the mass of diamond particles having any of the above-mentioned average particle sizes and distributions. The mass of diamond particles and the disk containing the catalyst material are placed in a pressuring transmitting device to form a cell assembly. The cell assembly is then subjected in an HPHT sintering process (e.g., a temperature of at least 1000° C. and a pressure of at least 5.0 GPa). The catalyst material from the disk infiltrates the mass of diamond particles and occupies at least a portion of the plurality of interstitial regions of the PCD table so formed.

The preformed PCD table may be machined following the HPHT sintering process. For example, the preformed PCD table may be machined to include a chamfer or may be machined to make a surface more planar or smooth. Additionally, the performed PCD table may have a patterned machined onto a surface. The pattern may be a grooved or ridged pattern. The pattern may be machined to form a series of concentric circles. The machining process may be performed using a lapping process, a grinding process or any suitable process.

In any of the embodiments described herein, at least a portion of the catalyst material may be removed (e.g., via leaching) from the PCD table. The catalyst material may be removed from the PCD table to increase the thermal stability of the PCD table. Additionally, the catalyst material may be removed from a preformed PCD table to facilitate remounting the preformed PCD table to a substrate 1204 during a second HPHT sintering process. In an embodiment, the catalyst material is substantially completely removed from the PCD table. For example, a preformed PCD table is immersed in an acid or solution, such as hydrochloric acid, nitric acid (e.g., aqua-regia, a solution of 90% nitric acid/10% de-ionized water), phosphoric acid, acetic acid, hydrofluoric acid, any suitable acid or any combination of acids. The preformed PCD table may be immersed in the acid for about 2 to 7 days (e.g., about 3, 5, or 7 days) or for a few weeks (e.g., about 4 weeks) depending on the process employed. In another embodiment, the infiltrant material in the PCD table may be removed to a selected depth from at least one surface (e.g., at least one of an upper surface, a lateral surface and a chamfer) of the PCD table so that only a portion of the infiltrant material may be removed from the PCD table. This may be performed by immersing only a portion of the PCD table in an acid or masking portions of the PDC with an acid resistant assembly.

In another embodiment, the leaching agent (e.g., an acid, base, any solution capable of removing the catalyst material, or combinations thereof) is selected such that the leaching agent selectively removes one infiltrant material without affecting other infiltrant materials.

In another embodiment, the leaching process only removes the catalyst material from a peripheral region of the PDC table, such as the mechanically-stressed PCD table 302 shown in FIG. 3. For example, the leach depth d that the peripheral region extends to may be about 50 gm to about 500 μm. such as greater than about 200 μm or greater than 400 μm.

In an embodiment, the PCD table 908 may be at least partially leached to deplete the PCD table of the catalyst material that previously occupied at least a portion of the interstitial regions thereof to define a first leached volume adjacent to the upper surface. The first leached volume exhibits a depth d as measured from one or more of the upper surface, at least one side surface, or a chamfer extending therebetween. The PCD table additionally includes a second volume remote from the upper surface that has not been leached so that at least a portion of the interstitial regions thereof are still occupied by the catalyst material. In an embodiment, the leach depth d that the first leach volume extends to may be about 50 μm to about 500 μm (e.g., greater than about 200 μm or greater than 400 μm). In another embodiment, the PCD table may be leached so that the leach depth d may be approximately equal to a thickness of the PCD table. The leaching agent used to remove the catalyst material may leave one or more types of residual salts, one or more types of oxides, combinations of the foregoing, or another leaching by-product within at least some of the interstitial regions of the at least partially leached preformed PCD table. At least some of the leaching by-products may be removed from the at least partially leached PCD table. Details about suitable cleaning techniques for removing the leaching by-products are disclosed in U.S. Pat. Nos. 7,845,438 and 7,845,438 is incorporated herein, in its entirety, by this reference.

The disclosed PDC embodiments may be used in a number of different applications including, but not limited to, use in a rotary drill bit (FIGS. 13A and 13B), a thrust-bearing apparatus (FIG. 14), a radial bearing apparatus (FIG. 15), a mining rotary drill bit (e.g., a roof bolt drill bit), and a wire-drawing die. The various applications discussed above are merely some examples of applications in which the PDC embodiments may be used. Other applications are contemplated, such as employing the disclosed PDC embodiments in friction stir welding tools.

FIG. 13A is an isometric view and FIG. 13B is a top plan view of an embodiment of a rotary drill bit 1300 for use in subterranean drilling applications, such as oil and gas exploration. The rotary drill bit 1300 includes at least one PCD element and/or PDC configured according to any of the previously described PDC embodiments. The rotary drill bit 1300 comprises a bit body 1302 that includes radially and longitudinally extending blades 1304 with leading faces 1306, and a threaded pin connection 1308 for connecting the bit body 1302 to a drilling string. The bit body 1302 defines a leading end structure for drilling into a subterranean formation by rotation about a longitudinal axis and application of weight-on-bit. At least one PDC cutting element, configured according to any of the previously described PDC embodiments may be affixed to the bit body 1302. With reference to FIG. 13B, a plurality of PDCs 1312 are secured to the blades 1304. For example, each PDC 1312 may include a PCD table 1314 bonded to a substrate 1316. More generally, the PDCs 1312 may comprise any PDC disclosed herein, without limitation. In addition, if desired, in some embodiments, a number of the PDCs 1312 may be conventional in construction. Also, circumferentially adjacent blades 1304 define so-called junk slots 1318 therebetween, as known in the art. Additionally, the rotary drill bit 1300 may include a plurality of nozzle cavities 1320 for communicating drilling fluid from the interior of the rotary drill bit 1300 to the PDCs 1312.

FIG. 14 is an isometric cut-away view of an embodiment of a thrust-bearing apparatus 1400, which may utilize any of the disclosed PDC embodiments as bearing elements. The thrust-bearing apparatus 1400 includes respective thrust-bearing assemblies 1402. Each thrust-bearing assembly 1402 includes an annular support ring 1404 that may be fabricated from a material, such as carbon steel, stainless steel, or another suitable material. Each support ring 1404 includes a plurality of recesses (not labeled) that receives a corresponding bearing element 1406. Each bearing element 1406 may be attached to a corresponding support ring 1404 within a corresponding recess by brazing, press-fitting, using fasteners, or another suitable mounting technique. One or more, or all of bearing elements 1406 may be configured according to any of the disclosed PDC embodiments. For example, each bearing element 1406 may include a substrate 1408 and a PCD table 1410, with the PCD table 1410 including a bearing surface 1412.

In use, the bearing surfaces 1412 of one of the thrust-bearing assemblies 1402 bears against the opposing bearing surfaces 1412 of the other one of the thrust-bearing assemblies 1402. For example, one of the thrust-bearing assemblies 1402 may be operably coupled to a shaft to rotate therewith and may be termed a “rotor.” The other one of the thrust-bearing assemblies 1402 may be held stationary and may be termed a “stator.”

FIG. 15 is an isometric cut-away view of an embodiment of a radial bearing apparatus 1500, which may utilize any of the disclosed PDC embodiments as bearing elements. The radial bearing apparatus 1500 includes an inner race 1502 positioned generally within an outer race 1504. The outer race 1504 includes a plurality of bearing elements 1510 affixed thereto that have respective bearing surfaces 1512. The inner race 1502 also includes a plurality of bearing elements 1506 affixed thereto that have respective bearing surfaces 1508. One or more, or all of the bearing elements 1506 and 1510 may be configured according to any of the PDC embodiments disclosed herein. The inner race 1502 is positioned generally within the outer race 1504 and, thus, the inner race 1502 and outer race 1504 may be configured so that the bearing surfaces 1508 and 1512 may at least partially contact one another and move relative to each other as the inner race 1502 and outer race 1504 rotate relative to each other during use.

The radial bearing apparatus 1500 may be employed in a variety of mechanical applications. For example, so-called “roller cone” rotary drill bits may benefit from the radial bearing apparatus disclosed 1500 herein. More specifically, the inner race 1502 may be mounted to a spindle of a roller cone and the outer race 1504 may be mounted to an inner bore formed within a cone and that such an outer race 1504 and inner race 1502 may be assembled to form a radial bearing apparatus.

While various aspects and embodiments have been disclosed herein, other aspects and embodiments are contemplated. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting. Additionally, the words “including,” “having,” and variants thereof (e.g., “includes” and “has”) as used herein, including the claims, shall be open ended and have the same meaning as the word “comprising” and variants thereof (e.g., “comprise” and “comprises”). 

1. A polycrystalline diamond compact, comprising: a substrate including an interfacial surface; and a mechanically-stressed polycrystalline diamond table coupled to the substrate, the mechanically-stressed polycrystalline diamond table including an upper surface spaced from a bottom surface that faces the interfacial surface of the substrate, the upper surface of the mechanically-stressed polycrystalline diamond table exhibiting a mechanical deflection and a concave curvature induced by forced contact between the bottom surface of the mechanically-stressed polycrystalline diamond table and the interfacial surface of the substrate, the forced contact comprising applying a forcing element to the upper surface under sufficient temperature and pressure to bend the polycrystalline diamond table into contact with the interfacial surface of the substrate; wherein, prior to the forced contact, the mechanically-stressed polycrystalline diamond table is not coupled to the substrate.
 2. The polycrystalline diamond compact of claim 1, wherein, prior to the forced contact, the bottom surface of the mechanically-stressed polycrystalline diamond table and a portion of the substrate at least partially define a region into which the bottom surface of the mechanically-stressed polycrystalline diamond table is deflected.
 3. The polycrystalline diamond compact of claim 1, wherein the bottom surface of the mechanically-stressed polycrystalline diamond table contacts the interfacial surface of the substrate such that the bottom surface of the mechanically-stressed polycrystalline diamond table contacts substantially the entire interfacial surface of the substrate.
 4. The polycrystalline diamond compact of claim 1, wherein the interfacial surface of the substrate exhibits a concave curvature.
 5. The polycrystalline diamond compact of claim 1, wherein the forcing element comprises a mechanical fastener that couples the mechanically-stressed polycrystalline diamond table to the substrate.
 6. The polycrystalline diamond compact of claim 5, further comprising a washer positioned between a top portion of the mechanical fastener and the upper surface of the mechanically-stressed polycrystalline diamond table.
 7. The polycrystalline diamond compact of claim 5, wherein each of the mechanically-stressed polycrystalline diamond table and the substrate includes an aperture extending therethrough that receives the mechanical fastener.
 8. The polycrystalline diamond compact of claim 1, further comprising a washer including an upper washer surface that contacts the bottom surface of the mechanically-stressed polycrystalline diamond table and a bottom washer surface that contacts at least one of the interfacial surface of the substrate or an upper surface of a second polycrystalline diamond table.
 9. The polycrystalline diamond compact of claim 1, wherein each of the bottom surface of the mechanically-stressed polycrystalline diamond table and the interfacial surface of the substrate has a pattern thereon.
 10. The polycrystalline diamond compact of claim 1, wherein the mechanically-stressed polycrystalline diamond table includes a leached region extending inwardly from the upper surface thereof from which at least a portion of a catalyst is removed.
 11. The polycrystalline diamond compact of claim 1, wherein the substrate includes an outer region exhibiting a first modulus of elasticity and an inner region exhibiting a second modulus of elasticity less than the first modulus of elasticity.
 12. The polycrystalline diamond compact of claim 1, further comprising at least one second polycrystalline diamond table, wherein the mechanically-stressed polycrystalline diamond table and the at least one second polycrystalline diamond table form a plurality of stacked polycrystalline diamond tables that are coupled to the substrate.
 13. The polycrystalline diamond compact of claim 12, wherein the plurality of stacked polycrystalline diamond tables are bonded together.
 14. The polycrystalline diamond compact of claim 1, wherein the mechanically-stressed polycrystalline diamond table is brazed to the substrate.
 15. The polycrystalline diamond compact of claim 1, wherein the mechanically-stressed polycrystalline diamond table exhibits a thickness of from 0.120 inches to 0.400 inches.
 16. The polycrystalline diamond compact of claim 1, wherein the mechanically-stressed polycrystalline diamond table includes a first region that extends inwardly from every surface of the polycrystalline diamond table, and a second region that is remote from every surface of the polycrystalline diamond table, wherein the first region has been leached to remove at least some of a catalyst therein and the second region is substantially unleached.
 17. A method of forming a polycrystalline diamond compact, the method comprising: providing an at least partially leached polycrystalline diamond table including an upper surface and a bottom surface; and deflecting the at least partially leached polycrystalline diamond table to form a mechanically-stressed polycrystalline diamond table, the upper surface of the mechanically-stressed polycrystalline diamond table exhibiting a mechanical deflection and a concave curvature induced by forcing contact between the bottom surface of the at least partially leached polycrystalline diamond table and an interfacial surface of a substrate, the forcing contact comprising applying a forcing element to the upper surface under sufficient temperature and pressure to bend the polycrystalline diamond table into contact with the interfacial surface fo the substrate; wherein, prior to forcing contact, the at least partially leached polycrystalline diamond table is not coupled to the substrate.
 18. The method of claim 17, further comprising subjecting the at least partially leached polycrystalline diamond table positioned adjacent to the substrate to a high-pressure/high-temperature process effective to infiltrate the at least partially leached polycrystalline diamond table with an infiltrant from the substrate and bond the mechanically-stressed polycrystalline diamond table to the substrate.
 19. The method of claim 17, wherein deflecting the at least partially leached polycrystalline diamond table to form the mechanically-stressed polycrystalline diamond table includes deflecting the at least partially leached polycrystalline diamond table toward the substrate during a high-pressure/high-temperature process.
 20. The method of claim 17, wherein forcing element comprises a mechanical fastener.
 21. The method of claim 17, further comprising brazing the at least partially leached polycrystalline diamond table to the substrate.
 22. The method of claim 17, further comprising brazing the at least partially leached polycrystalline diamond table to a second polycrystalline diamond table.
 23. A rotary drill bit, comprising: a bit body configured to engage a subterranean formation; and a plurality of polycrystalline diamond cutting elements attached to the bit body, at least one of the plurality of polycrystalline diamond cutting elements including: a substrate including an interfacial surface; and a mechanically-stressed polycrystalline diamond table coupled to the substrate, the mechanically-stressed polycrystalline diamond table including an upper surface spaced from a bottom surface that faces the interfacial surface of the substrate, the upper surface of the mechanically-stressed polycrystalline diamond table exhibiting mechanical deflection induced by forced contact between the bottom surface of the mechanically-stressed polycrystalline diamond table and the interfacial surface of the substrate, the forced contact comprising applying a forcing element to the upper surface under sufficient temperature and pressure to bend the polycrystalline diamond table into contact with the interfacial surface of the substrate; wherein, prior to the forced contact, the mechanically-stressed polycrystalline diamond table is not coupled to the substrate.
 24. The rotary drill bit of claim 23, further comprising at least one fastener that couples the at least one of the plurality of polycrystalline diamond cutting elements to the bit body and the mechanically-stressed polycrystalline diamond table to the substrate.
 25. The rotary drill bit of claim 23, wherein the at least one of the plurality of polycrystalline diamond cutting elements is brazed to the bit body. 